GREATER FUNDY ECOSYSTEM RESEARCH PROJECT

UNB Faculty of Forestry and Environmental Management

State of the Greater Fundy Ecosystem

Annotated Bibliography on
Cavity-nesting Birds research (1992-1997)

Albano, D.J. 1992. Nesting mortality of Carolina Chickadees breeding in natural cavities. Condor 94: 371-382.

This study documents nesting mortality within a southern Illinois population of Carolina Chickadees breeding in natural cavities and relates variation in mortality with variation in nest-hole structure and microclimate. Little variation in nest-hole structure and microclimate and little variation in air-nest temperature differentials was found among nests and variations in nest-hole structure was not strongly correlated with variations in any of the indices of insulative variation. No total nest failures were attributable to ambient extremes. Predation was the greatest influence on nesting success, accounting for every case of total nest-loss and 78.7% of all egg and chick mortality. Nests excavated nearer the ground and in softer wood were preyed upon significantly more than higher or more solidly-housed nests. It is suggested that chickadees may compensate for their low ranking status among larger, more aggressive hole-nesting species by their great nest-site selection plasticity as well as their ability to rapidly renest following nest destruction.

Allen, P.E. 1996. Breeding biology and natural history of the Bahama Swallow. Wilson Bull. 108(3): 480-495.

The near-threatened status of this poorly known species stems from limited extent of pine forest breeding habitat, a history of logging in that habitat, and potential competition from exotic secondary cavity-nesters. Natural nest sites of this bird on Grand Bahama generally were abandoned woodpecker cavities and nests in all types of cavities were built from pine needles, twigs, and grass. Hatching success was 70% overall.

Alworth, T. 1996. An experimental test of the function of sticks in the nests of House Wrens. Condor 98: 841-844.

By preventing males from filling treatment nest boxes with sticks, the study tested two hypothesis. First, if filling a nest box with sticks by males is necessary for courtship and mating, the stick removal from boxes should preclude pair-bond formation. Second, if having a stick foundation enhances fledgling success in some way, than pairs with sticks removed should be less successful in rearing and fledging young. Removing sticks from the nests of House Wrens had little effect on pair-bond formation, nesting stage duration, number of eggs laid or young fledged, therefore their function remains unclear.

Andersen, M.C. and D. Mahato. 1995. Demographic model and reserve designs for the California Spotted Owl. Ecol. Appl. 5(3): 639-647

Anderson, D.J., J. Reeve, J.E.M. Gomez, W.W. Weathers, S. Hutson, H.V. Cunningham, and D.M. Bird. 1993. Sexual size dimorphism and food requirements of nestling birds. Can. J. Zool. 71: 2541-2545.

The food requirements of dependent sons and daughters have important implications for evolution of the sex ratio, according to current sex allocation theory. The researchers studied food requirements of nestling American Kestrels by hand feeding 61 birds from hatching to fledging. Daughters, the larger gender, consumed 6.99% more food than did sons. Sons did not have higher energy expenditure from higher effort during sibling competition than daughters did, so parents must supply more food to satisfy daughters' needs than to satisfy sons'. A review of all related studies shows a strong positive association between the degree of sexual size dimorphism and gender difference in food requirements.

Anderson, T.R. 1995. Removal indetermining and the proximate determination of clutch size in the House Sparrow. Condor 97: 197-207.

Andries, A.M., H. Gulinck and M. Herremans. 1994. Spatial modeling of the Barn Owl Tyto alba habitat using landscape characteristics derived from SPOT data. Ecography 17: 278-287.

Angelstam, P. and G. Mikusinski. 1994. Woodpecker assemblages in natural and managed boreal and hemiboreal forest - a review. Ann. Zool. Fennici 31:157-172.

Arnold, T.W. 1993. Fledging success in experimentally manipulated broods of House Wrens. Wilson Bull. 105(3): 448-454.

This study featured manipulation of brood size in a population of box-nesting House Wrens to determine if fledging success was limited by the ability of parents to provision nestlings. Enlarged broods produced significantly more fledged young than did control or reduced broods, but fledglings from enlarged broods weighed 6-7% less than fledglings from other broods. The results do not support the brood-provisioning hypothesis. Brood size in House Wrens may be limited by post-fledging survival or interseasonal costs of reproduction but this study was unable to determine this.

Arnold, T.W. and P.A. Martin. 1992. Winter habitat use by male and female American Kestrels, Falco sparverius, in Southwestern Ontario. Canadian Field-Naturalist 106(3): 336-341

Throughout much of the southern U.S. and Mexico, wintering American Kestrels exhibit sexual segregation by habitat, with females occupying areas that are relatively more open and males occupying areas that are relatively more wooded. This study investigated habitat use by wintering Kestrels in southern Ontario. It detected no differences in habitat selection between males and females. This may have been due to low densities of wintering Kestrels and hence little intersexual competition for high quality (i.e. more open) habitats.

Baggett, D.L. 1995. Improved installation of artificial cavities for Red-cockaded Woodpeckers. Wildl. Soc. Bull. 23(1): 101-102.

The researchers describe an alternative to climbing ladder to access trees for installation of prefabricated cavity inserts. A portable bucket lift elevates the technician beside the selected tree, providing a safe platform from which to work while installing the artificial cavity.

Bancroft, G.T., A.M. Strong, and M. Carrington. 1995. Deforestation and its effects on forest-nesting birds in the Florida Keys. Conserv. Biol. 9(4): 835-844.

Prior to European settlement, there were 4816 ha of seasonal deciduous forest in the Florida Keys. By 1991, the extent of this seasonal deciduous forest had decreased by 41%, the number of fragments increased by an order of magnitude , and the acreage in large fragments decreased by 84%. To examine the effects of fragment size on the presence of breeding birds, the researchers censused bird populations of singing males that occurred in 27 forests that ranged in size from 0.2 ha to more than 100 ha. The study also examined the occurrence of forest-breeding species at road-stop census points relative to none measures of habitat around these points. The distribution of Red-bellied Woodpeckers occurred independently of the size of forest fragments but was positively correlated with other measures of forest area. Northern Flickers were not present in fragments smaller than 3.5 ha, but their numbers showed the highest positive correlation with the percentage of areas in lawns and were negatively correlated with measures of total forest area. To maintain the viable populations of species native to the seasonal deciduous forests of the Florida Keys will require protection of additional acreage of upland habitat from deforestation. A network of reserves that maintains dispersal possibilities among the remaining larger forest fragments is crucial.

Bart, J. 1995. Amount of suitable habitat and viability of Northern Spotted Owls. Conserv. Biol. 9(4): 943-946.

This paper comments on the rationales used by the U.S. Fish and Wildlife Service to develop a series of guidelines to protect Northern Spotted Owls from harm due to harvest of old-growth trees in proximity to nests or activity centres. Several suggestions are offered for improving the guidelines.

Benitez-Diaz, H. 1993. Geographic variation in coloration and morphology of the Acorn Woodpecker. Condor 95: 63-71.

Berbach, M. and R. Motroni. 1994. A Northern Spotted Owl habitat conservation plan for California: status and lessons learned. Trans. West. Sect. Wildl. Soc. 30: 56-65

Bernstein, C., J.R. Krebs, and A. Kacelnik. 1994. Distribution of birds amongst habitats: theory and relevance to conservation. In: C.M. Perrins, J.D. Lebreton, and G.J.M. Hirons (eds.) Collected papers of the first international symposium organized by the "Station Biologique de la Tour du Valat" Dec 12-16, 1988. Arles, France.

Bias, M.A. and R.J. Gutierrez. 1992. Habitat associations of California Spotted Owls in the central Sierra Nevada. J. Wildl. Manage. 56(3): 584-595.

Blake, J.G., J.M. Hanowski, G.J. Niemi, and P.T. Collins. 1994. Annual variation in bird populations of mixed conifer-northern hardwood forests. Condor 96: 381-399.

Examination of annual variation in breeding bird populations at sites in northwestern Wisconsin and upper Michigan from 1986-92 to determine (1) the extent to which different bird species vary in abundance over time and (2) whether or not patterns of variation differ when viewed at local and regional spatial scales. Results of this study illustrate the importance of considering temporal variation in abundance at more than one spatial scale.

Bledsoe, A.H., R.J. Raikow, and L.S. Crowell. 1997. Intraspecific variation and evolutionary reduction of tendon ossification in Dendrocinda Woodcreepers. Condor 99: 503-511.

Blem, C.R. and L.B. Blem. 1994. Composition and microclimate of Prothonotary Warbler nests. Auk 111(1): 197-200.

Studies of Prothonotary Warblers nesting in artificial nest boxes, suggest that physical environment affects nesting by this species. First, multivariate analyses of nesting habitat indicate that Prothonotary Warblers prefer nest boxes in shaded areas near water and avoid boxes in open, sunny areas. Second, they build distinctive nests consisting of a dry cup (grasses, leaves, and rootlets) on a thick bed of moist, green bryophytes. We suspect the composition of the nests affects the environment within the nest cavity. The observations suggest that Prothonotary Warblers early in the breeding season work on nests in more than one cavity at a time, but eventually only select one nest to complete. Partial nests have been considered to be "dummy" nests constructed perhaps for the purpose of confusing predators. It is also possible that the birds detect differences in temperature between boxes in the process of selecting a cavity.

Bortolotti, G.R. 1994. Effects of nest-box size on nest-site preference and reproduction in American Kestrels. J. Raptor Res. 28(3): 127-133.

Bortolotti, G.R. and J.R. Gabrielson. 1995. Fluctuating asymmetry in the skeleton of the American Kestrel, Falco sparverins: a test of the consequences of sexual size dimorphism. Can. J. Zool. 73: 141-145.

Brun, J. and T. Lubjuhn. 1993. Automatic measuring of sex-specific visiting rates to nests in hole-breeding avian species. Auk 110(4): 953-954.

Description of a device to count nest visits of hole breeders automatically and for the sexes separately. The device consists of three subunits: (1) two light barriers that enable one to count every nest visit regardless of sex; (2) a metal detector that counts only visits of one parent previously banded; (3) two registration modules that store the number of visits detected by each of the above mentioned subunits. The light barriers and the metal detector are placed in the entrance of the nest box , while the registration modules and a 12-V power supply are placed in a separate box below. The registration modules must be read from time to time by looking at the digital displays and then reset to zero.

Buchanan, J.B., L.L. Irwin, and E.L. McCutchen. 1995. Within-stand nest site selection by Spotted Owls in the eastern Washington Cascades. J. Wildl. Manage. 59(2): 301-310.

Cade, T.J. and C.G. Jones. 1993. Progress in restoration of the Mauritius Kestrel. Conservation Biology 7(1): 169-175.

Since 1984, 139 young have been reared from 618 eggs laid by captive kestrels, and 147 from 265 wild eggs incubated and hatched in the laboratory; 235 young kestrels have been released on Mauritius by hacking and fostering. Adjustments in feeding and nesting habits of kestrels hacked and released outside the Black River Gorges in areas dominated by exotic vegetation and agriculture have allowed these kestrels in survive and reproduce in an array of previously unused habitats. Now that the kestrels have been released from dependence on the remnant and dying native forest, a viable population of more than 100 nesting pairs should be achievable in a few more years.

Call, D.R., R.J. Gutierrez and J.Verner. 1992. Foraging habitat and home-range characteristics of California Spotted Owls in the Sierra Nevada. Condor 94: 880-888.

Examined habitat use patterns at two spatial scales among six radio-tagged California Spotted Owls in the Sierra Nevada. Foraging owls selected microhabitat composed of larger trees (> 52 cm dbh) with canopy closures of 40% or greater. Owls used forests composed of medium trees (28-52 cm dbh) and habitats with less than 40% canopy closure. Fewer than 2% of telemetry locations occurred in clearcut/shrub/plantation habitat which represented 30% of available habitat. Foraging owls used microhabitats that were characterized by multiple vegetative strata, large tree size classes, high tree basal areas and woody debris. The median 100% minimum convex polygon home-range was 1,439 ha. Estimates of minimum convex polygon and modified minimum convex polygon size based on statistically independent telemetry data were significantly smaller than estimates based on continuous and single-observation monitoring.

Cameron, R. 1996. Wildlife use of cavity tree clumps in clearcuts. Canadian Forest Service. R&D Report No.13. Fredericton, N.B.

Carey, A.B. 1995. Spotted Owl ecology: theory and methodology - a reply to Resenberg et al. Ecology 76(2): 648-652.

Carey, A.B., Horton, S.P. and Biswell, B.L. 1992. Northern Spotted Owls: influence of prey base and landscape pattern. Ecol. Monogr. 62: 223-250.

Carlson, A. and G. Aulen. 1992. Territorial dynamics in an isolated White-backed Woodpecker (Dendrocopos leucotos) population. Conservation Biology 6(3): 450-454.

An analysis of the spatial arrangement of White-backed Woodpecker territories in what appears to constitute a metapopulation. The intention is to explore differences in rates of extinction, colonization, and persistence of a population between an area with a low density of suitable habitat patches and an area with a higher density of such patches.

Carpenter, T.W. and A.L. Carpenter. 1993. Temporal differences in size of Northern Saw-whet Owls during spring migration. Wilson Bull. 105(2): 356-359.

Northern Saw-whet Owls exhibit reversed sexual size dimorphism, males being smaller than females. We used regression analysis to examine sex differences in the timing of spring migration of this owl in Michigan. Because of sexual size dimorphism, if differential timing by sex occurs, the regression should detect a relationship between time of migration and size.

Cassirer, E.F., G. Schirato, F. Sharpe, C.R. Groves. 1993. Cavity nesting by Harlequin Ducks in the Pacific Northwest. Wilson Bull. 105(4): 691-694.

The lack of adequate data from areas outside Iceland, and conflicts in old records, have led to disagreement as to whether Harlequin Ducks are cavity nesters or whether they primarily are ground nesters, nesting occasionally in areas sheltered by rocks or woody debris. This paper describes three Harlequin Duck cavity nests discovered in 1991 in northern Idaho and northwestern Washington. Two were in tree cavities and a third was in a rock cavity in a cliff face. These nests establish Harlequin Ducks as both cavity and ground nesters. Although ground nesting occurred in both study areas, Harlequin Ducks also nested in tree and cliff cavities when available, even when located 14 m from water and nearly 25 m from the main stream channel.

Clemmons, J.R. 1994. Multiple cases of polygyny in the Black-capped Chickadee: A possible advantage to the primary female. Condor 96: 1113-1114.

Report on several cases of bigyny occurring during one breeding season within a small study area

Clemmons, J.R. 1995. Vocalizations and other stimuli that elicit gaping in nestling Black-capped Chickadees (Parus atricapillus). Auk 112(3): 603-612.

Vocalizations of Black-capped Chickadees were analyzed by audio and video recordings within the nesting cavity. The parents' vocalization plays an important role in coupling the nestlings' gaping response with the appropriate situation, especially during the first days posthatching when nestling responses are coarsely tuned to appropriate stimuli.

Clemmons, J.R. and M.M. Lambrechts. 1992. The waving display and other nest site anti-predator behavior of the Black-capped Chickadee. Wilson Bull. 104(4): 749-756

Conner, R.N., S.D. Jones, and G.D. Jones. 1994. Snag conditions and woodpecker foraging ecology in a bottomland hardwood forest. Wilson Bull. 106(2): 242-257.

Study of woodpecker foraging behaviour, snag quality, and surrounding habitat in a bottomland hardwood forest. Woodpeckers excavated mainly at the well-decayed tops and bases of snags. Woodpeckers preferred to forage on oaks (snags and live trees) whereas blue beech and red maple were used less than expected. Snags used for foraging excavations were generally 3-10 m in height, mainly located in older stands, and lacked bark at excavated foraging sites. Downy Woodpeckers foraged on smaller diameter substrates and used more tree species than other woodpecker species. Pileated Woodpeckers foraged either near the ground or in the upper zones of trees. Red-bellied Woodpeckers used a restricted range of tree diameters and locations in trees. Red-headed Woodpeckers used the greatest diversity of foraging methods and foraged on the largest range of tree diameters.

Conner, R.N. and D.C. Rudolph. 1995. Losses of Red-cockaded Woodpecker cavity trees to Southern Pine beetles. Wilson Bull. 107(1): 81-92.

Conner, R.N. and D. Saenz. 1996. Woodpecker excavation and use of cavities in polystyrene snags. Wilson Bull. 108(3): 449-456.

Examination of woodpecker excavation and use of artificial polystyrene snags in four forest types in eastern Texas for five years. Twenty-three of 47 artificial snags were used by Downy Woodpeckers for cavity excavation and subsequent nocturnal roosting: they did not use the artificial snags for nesting. Although six other species of woodpeckers were present in the area, only Downy Woodpeckers excavated cavities in the artificial cavity substrate. Entrances to cavities in artificial snags became enlarged within several months of excavation. Other species using abandoned cavities in artificial snags were Carolina Chickadees, Prothonotary Warblers, Southern Flying Squirrels, and Red Wasps. In one instance, Carolina Chickadees excavated their own cavity and nested within a polystyrene snag. Until an artificial cavity substrate acceptable for both woodpecker excavation and nesting can be found, the utility of artificial snags as a means of augmenting woodpecker nesting substrate remains inadequate.

Conner, R.N., D.C. Rudolph, D. Saenz, and R.R. Schaefer. 1996. Red-cockaded Woodpecker nesting success, forest structure, and Southern Flying Squirrels in Texas. Wilson Bull. 108(4): 697-711.

General opinion has suggested that Southern Flying Squirrels have a negative effect on Red-cockaded Woodpeckers through competition for cavities and egg/nesting predation. Complete removal of hardwood trees from Red-cockaded Woodpecker cavity tree clusters has occurred on some forests because Southern Flying Squirrel abundance was presumed to be associated with the presence and abundance of hardwood vegetation. We determined Southern Flying Squirrel occupancy of Red-cockaded Woodpecker cavities in loblolly-shortleaf pine habitat (with and without hardwood mid-story vegetation) and longleaf pine habitat (nearly devoid of hardwood vegetation) during spring, late summer, and winter during 1990 and 1991. Flying squirrel use of Red-cockaded Woodpecker cavities was variable and was not related to presence or abundance of hardwood vegetation. Woodpecker nest productivity was not correlated with flying squirrel use of woodpecker cavities within clusters. We observed only six instances where Red-cockaded Woodpeckers successfully nested while flying squirrels occupied other cavities in the same tree. Our results suggest that complete removal of hardwoods from woodpecker cluster areas in loblolly and shortleaf pine habitat may not provide benefits to the woodpeckers through reduction of flying squirrel numbers. Reduction of hardwood mid-story around cavity trees, however, is still essential because of the woodpecker's apparent innate intolerance of hardwood mid-story foliage.

Cooper, H.D., C.M. Raley and K.B. Aubry. 1995. A noose trap for capturing Pileated Woodpeckers. Wildl. Soc. Bull. 23(2): 208-211.

The researchers report that a major advantage of this trapping technique is that is can be applied throughout the year and does not require Pileated Woodpeckers to enter cavities. Noose traps were tested on the Olympic Peninsula near Forks, Washington during summer and late fall 1992, summer 1993 and summer 1994.

Cooper, S.J. and D.L. Swanson. 1994. Seasonal acclimatization of thermoregulation in the Black-capped Chickadee. Condor 96: 638-646.

Black-capped Chickadees show seasonal metabolic acclimatization similar to, or greater than, other temperate wintering passerines in addition to behavioural adaptations and nocturnal hypothermia.

Cordero, P.J. 1993. Factors influencing numbers of syntopic House Sparrows and Eurasian Tree Sparrows on farms. Auk 110(2): 382-385.

Study to determine the effects of different habitat variables on the breeding numbers of both House and Eurasian Tree Sparrows on farms and at rural residences.

Daily, G.C. 1993. Heartwood decay and vertical distribution of Red-naped Sapsucker nest cavities. Wilson Bull. 105(4): 674-679.

Description of the dynamic spatial pattern of Red-naped Sapsucker cavity excavation in aspen groves and evaluation of the possible importance of heartwood decay distribution, a prerequisite for nesting excavation, in producing it. Sapsuckers typically situate the first cavity excavation in a tree relatively close to the ground and then make progressively higher excavations in subsequent years. Heartwood decay is reported to infect aspen via the roots or broken branch stubs, mostly at the base of trees. Coring revealed that all nest trees were rotted at the base. The pattern of sapsucker cavity excavation can be explained as the outcome of an interaction between the distribution over height within trees of both heart rot and predation risk.

Daan, S., C. Deerenberg and C. Dijkstra. 1996. Increased daily work precipitates natural death in the kestrel. J. Animal Ecol. 65: 539-544.

Kestrel parents in these experiments have been shown to adjust their daily energy expenditure to the modified brood size. Increased parental effort in this species thus entails an increased risk of death half a year later.

Darveau, M., P. Beauchesne, L. Belanger, J. Huot, and P. LaRue. 1995. Riparian forest strips as habitat for breeding birds in boreal forest. J. Wildl. Manage. 59(1): 67-78.

Davidar, P. and E.S. Morton. 1993. Living with parasites: Prevalence of a blood parasite and its effects on survivorship in the Purple Martin. Auk 110(1): 109-116.

Study of the prevalence of the blood parasite Haemoproteus prognei from 1986 to 1990 in a breeding colony of Purple Martins in Maryland and in overwintering martins in three Brazilian roosts in 1990.

Dellasala, D.A., J.C. Hagar, K.A. Engel, W.C. McComb, R.L. Fairbanks, and E.G. Campbell. 1996. Effects of silvicultural modifications of temperate rainforests on breeding and wintering bird communities, Prince of Wales Island, Southeast Alaska. Condor 98: 706-721.

Inventory of breeding and wintering bird communities in four treatments of temperate rainforest on Prince of Wales Island, Alaska, during 1991-92 an 1992-93. The four forest treatments sampled included: (1) young growth (20 years) originating from clearcut logging with no silvicultural modification, (2) young growth (20 years) precommercially thinned along uniformly-spaced thinning grids, (3) young growth (20 years) with gaps in the overstory canopy created by felling trees in 0.05 ha openings, and (4) virgin old growth (>= 150 years). To enhance habitat for wintering and breeding birds we recommend: (1) thinning young growth along variable-spaced grids to create additional canopy layers and improve snow-intercept properties of young growth for canopy-foraging birds, (2) retention of old-growth clumps in clearcuts for bird species associated with old-growth structure, and (3) long-term conservation of old growth temperate rainforest for breeding and wintering birds positively associated with old growth.

Delotelle, R.S. and R.J. Epting. 1992. Reproduction of the Red-cockaded Woodpecker in Central Florida. Wilson Bull. 104(2): 285-294.

Red-cockaded Woodpeckers near the southern extreme of the species' range had a low fledging rate, high fledgling survivorship, and a high level of breeder experience and adult survivorship compared to other populations. Breeding male and female survivorship was 10% and 23% higher, respectively, than northern populations. Tenure of helpers was higher than other populations, apparently as a result of high adult survivorship. Reproductive success was correlated with breeder experience, outside intrusion rate, and territory size.

Desrochers, A. and S.J. Hannon. 1997. Gap crossing decisions by forest songbirds during the post-fledging period. Conservation Biology 11(5): 1204-1210.

Little is known about the reluctance of different species of birds to cross habitat gaps. The researchers studies this by inducing birds in the post-fledging period to cross gaps of varying widths and to choose between routes through woodland or across open areas by attracting them to a recording of mobbing calls by Chickadees. When given a choice of travelling through woodland or across a gap, the majority of respondents preferred woodland routes, even when they were three times longer than shortcuts in the open. However, species differed greatly in their response to gaps.

Dobkin, D.S., A.C. Rich, J.A. Pretare and W.H. Pyle. 1995. Nest-site relationships among cavity-nesting birds of riparian and snowpocket Aspen woodlands in the northwestern great basin. Condor 97(3): 694-707.

Examination of nest-site and nest cavity characteristics for six species of cavity-nesting birds in montane riparian and snowpocket aspen woodlands in the Great Basin. Live trees and snags with dbh >24 cm were favoured as nest sites by all species. Red-naped Sapsuckers and Northern Flickers provided different sizes of nest cavities for a suite of non-excavator species. Flickers preferentially nested in snags; Sapsuckers nested primarily in live trees, but used live trees and snags in proportion to their availabilities. Relative abundances of excavators and nonexcavators were associated positively with numbers of cavities. Nest site variables overlapped extensively among species; Tree Swallows relied heavily on Sapsuckers for provision of nest cavities, European Starlings and Mountain Bluebirds primarily used Flicker-excavated cavities, and House Wrens used nest cavities across the broadest range of nest-site characteristics. Orientation of nest-cavity entrances was strongly bimodal, with most facing east or southwest. Cavity entrances of species that foraged largely outside of riparian woodlands, were oriented toward woodland edges, in contrast to nest cavities used by species that foraged largely within riparian woodlands. Snowpocket woodlands were much more extensive than riparian aspen, but birds strongly preferred riparian aspen stands as nesting habitats, presumably due to the scarcity of large aspen in snowpockets. Nest cavities appear to be a limiting resource with high potential for interspecific nest-site competition in these woodlands.

Doherty, P.F., T.C. Grubb, Jr., and C.L. Bronson. 1996. Territories and caching-related behavior of Red-headed Woodpeckers wintering in a beech grove. Wilson Bull. 108(4): 740-747.

Description of caching and related behaviour of Red-headed Woodpeckers wintering in a beech grove during a mast year and relating territorial behaviour and territory size to territory-specific mast abundance. No difference was found between territories of adults and juveniles in either territory size or abundance of mast. Rates of caching and social interaction decreased over the course of the winter.

Duke, G.E., J. Reynhout, A.L. Tereick, A.E. Place and D.M. Bird. 1997. Gastrointestinal morphology and motility in American Kestrels receiving high or low fat diets. Condor 99: 123-131.

Dunn, P.O. and S.J. Hannon. 1992. Effects of food abundance and male parental care on reproductive success and monogamy in Tree Swallows. Auk 109(3): 488-499.

Examined roles of food abundance and male parental care in the maintenance of monogamy in Tree Swallows. Mated, male Tree Swallows were removed from territories to simulate the lack of parental care that would be incurred by secondary females. The results suggested that loss of male parental care had little effect on reproductive success or survival of females or their offspring. Unaided females increased their per-capita nest-visit rate.

Du Plessis, M.A., W.W. Weathers, and W.D. Koenig.1994. Energetic benefits of communal roosting by Acorn Woodpeckers during the non-breeding season. Condor 96: 631-637.

Examination of the thermal consequences, energy benefits and patterns of night-time communal roosting in Acorn Woodpeckers during the non-breeding season, the period when they are most reliant on nutrient-poor acorn stores. Energy savings of communal roosting may contribute to the higher winter survival noted for male Acorn Woodpeckers that live in larger groups.

Dykstra, C.R. and W.H. Karasov. 1993. Daily energy expenditure by nesting House Wrens. Condor 95: 1028-1030.

Daily energy expenditure of dependent chicks is important to birds since parent birds must apply all the energy which chicks use. This paper reports on the field metabolic rate of free-living House Wren nestlings age 11-14 days, measured with doubly labeled water.

Dykstra, C.R. and W.H. Karasov. 1993. Nesting energetics of House Wrens (Troglodytes aedon) in relation to maximal rates of energy flow. Auk 110(3): 481-491.

Eberhardt, L.S. 1997. A test of an environmental advertisement hypothesis for the function of drumming in Yellow-bellied Sapsuckers. Condor 99: 798-803.

Examination of the drum sites of Yellow-bellied Sapsuckers revealed that Sapsuckers do not use drumming to advertise the presence of nesting and feeding sites in their environment. In general, sapsuckers drummed in locations that could produce louder and longer lasting sounds than surrounding non-drum substrate including nest trees, feeding trees, and other substrate near the site of drumming. The researcher's evidence suggests that sapsucker drumming is an acoustic signal designed for long distance transmission.

Edenius, L. and J. Elmberg. 1996. Landscape level effects of modern forestry on bird communities in North Swedish boreal forests. Landscape Ecol. 11(6): 325-338.

Egan, E.S. and M.C. Brittingham. 1994. Winter survival rates of a southern population of Black-capped Chickadees. Wilson Bull. 106(3): 514-521.

Engstrom, R.T. and F.J. Sanders. 1997. Red-cockaded Woodpecker foraging ecology in an old-growth longleaf pine forest. Wilson Bull. 109(2): 203-217.

Year-round home range was negatively correlated with the percentage of the home-range located within old-growth forest. In the old-growth stand the size class distribution of trees selected by woodpeckers for foraging was different than the distribution of trees available in size classes >30 cm dbh. Red-cockaded Woodpeckers preferentially forage on large (and presumably old) trees. We suggest that forest management intended to provide adequate number of replacement cavity trees and quality foraging habitat for the Red-cockaded Woodpecker should have old trees across the landscape.

Evans, D.R. and J.E. Gates. 1997. Cowbird selection of breeding areas: the role of habitat and bird species abundance. Wilson Bull. 109(3): 470-480.

This study found that cowbirds in western Maryland select breeding areas based on: (1) distinct visible edges formed by canopy openings in the forest landscape, (2) occurrence of both high snag BA and high TVV at the forest edge, and (3) presence of high bird species abundance.

Farley, G.H., L.M. Ellis, J.N. Stuart, N.J.Scott Jr. 1994. Avian species richness in different-aged stands of riparian forest along the middle Rio Grande, New Mexico. Conservation Biology 8(4): 1098-1108.

In order to counteract loss of riparian forest habitat, several mitigation programs were developed in the middle Rio Grande Valley of New Mexico. Three areas ranging from 50 to 140 ha were re-vegetated with native trees using pole planting and cattle exclosures and changes in vegetation structure were quantified after 2,3, and 5 years of growth. As expected, the older site contained the most heterogeneous mix of plant species and the greatest structural diversity. The researchers compared year-round avian use of the re-vegetated sites with a mature cottonwood forest site of approximately 30 years of age. As the vegetated sites matured and salient habitat features changed, the population dynamics of individual avian species and patterns of guild structure varied. The older re-vegetated sites showed a greater similarity to the mature cottonwood site, suggesting that reclamation efforts established quality riparian habitats for birds. The researchers suggest that a mosaic of riparian woodlands containing mixtures of native tree and shrub species of different size classes is necessary to maintain avian species richness in the middle Rio Grande drainage, and probably throughout the southwestern U.S.

Flaspohler, D.J. 1996. Nesting success of the Prothonotary Warbler in the Upper Mississippi River bottomlands. Wilson Bull. 108(3): 457-466.

Study of the breeding biology and nesting success of Prothonotary Warblers at the margin of the species' breeding range on the upper Mississippi and Black rivers in west-central Wisconsin. Observed effects of flooding, cowbird parasitism and nest destruction by House Wrens.

Fletcher, S.D. and W.S. Moore. 1992. Further analysis of allozyme variation in the Northern Flicker, in comparison with mitochondrial DNA variation. Condor 94: 988-991.

Forsman, E.D. and A.R. Giese. 1997. Nests of Northern Spotted Owls on the Olympic Peninsula, Washington. Wilson Bull. 109(1): 28-41.

One hundred and fifty-five nests were located on the Olympic Peninsula, all of which were in trees. One hundred and five of these nests were in cavities. Cavity nests were typically in large holes in the side of the trunk or in the broken tops of the trunk. The majority of cavities faced east-northeast. Nests usually were in stands with high overall canopy closure (>= 70%) but canopy closure in the immediate vicinity of the nest varied from 35-90%. Most nests were in multi-layered stands dominated by large trees. Nests in younger stands were typically in stands where remnant old trees were present.

Fotheringham, J.R. and L. Ratcliffe. 1996. Song degradation and estimation of acoustic distance in Black-capped Chickadees (Parus atricapillus). Can. J. Zool. 73: 858-868.

Fournier, M.A. and J.E. Hines. 1996. Changed status of the Hooded Merganser, Lophodytes cucullatus, in the Yellowknife area, Northwest Territories. Canadian Field-Naturalist 110(4): 713-714.

Freedman, B., S. Woodley, and J. Loo. 1994. Forestry practices and biodiversity, with particular reference to the Maritime Provinces of eastern Canada. Environ. Rev. 2:33-77.

This report discusses interactions of forestry at three levels of organization: i) genetic variation within populations and species; ii) the richness of species within communities; and, iii) the richness of community types on the landscape. Bird species dependent on deadwood and cavities are discussed. A broader conclusion of the report is: If forestry systems of harvesting and management are to be practiced in an ecologically sustainable fashion, then all elements of biodiversity must be accommodated within a landscape comprised of an integration of working lands and ecological reserves. The spatial scale of this integration could be various, ranging from large watersheds, to the "woodsheds" of particular industrial facilities, to provincial and national areas. Therefore, resolution of the substantial conflicts between biodiversity and forestry requires the design of ecologically sustainable landscapes that can provide a flow of timber and other valuated forest products, while still sustaining natural biodiversity resources.

Galeotti, P. 1994. Patterns of territory size and defense level in rural and urban Tawny Owl (Strix aluco) populations. J. Zool. Lond. 234: 641-658.

Gehlbach, F.R. 1994. Nest-box versus natural-cavity nests of the Eastern Screech-Owl: an exploratory study. J. Raptor Res. 28(3): 154-157.

Gerhardt, R.P., N.B. Gonzalez, D.M. Gerhardt, and C.J. Flatten. 1994. Breeding biology and home range of two Ciccaba owls. Wilson Bull. 106(4): 629-639.

Gionfriddo, J.P. and L.B. Best. 1995. Grit use by House Sparrows: Effects of diet and grit size. Condor 97: 57-67.

Greenberg, C.H., L.D. Harris, and D.G. Neary. 1995. A comparison of bird communities in burned and salvage-logged, clearcut, and forested Florida sand pine scrub. Wilson Bull. 107(1): 40-54.

Comparison of bird communities of sand pine scrub in mature forest and three disturbance treatments: 1) high-intensity wildfire, salvage logged, and naturally regenerated; 2) clearcut, roller chopped, and broadcast seeded; and, 3) clearcut and bracheseeded. Migratory breeding birds were nearly restricted to mature forest. Bird communities of mature forest were significantly more species rich and diverse than those of disturbance treatments in spring. However, species richness and diversity of migratory winter residents did not differ among treatments, indicating that they are habitat-structure generalists on their wintering grounds. Canopy- and cavity-nesters and canopy- and bark-foraging species were virtually restricted to mature forest. Most species recorded in mature sand pine forests or disturbance treatments were either habitat-structure generalists or also occurred in other similarly structured vegetation types. Silvicultural disturbance appears to mimic the natural high-intensity disturbance regime by creating habitat structure features required by open scrub species and may be an important habitat management tool where the use of wildfire is impractical. However, long-term effects, unsalvaged burns and landscape patterns created by clearcutting were not addressed and may also be important in structuring bird communities of sand pine scrub.

Grubb, T.C., Jr., and C.L. Bronson. 1995. Artificial snags as nesting sites for chickadees. Condor 97: 1067-1070.

Description of an introduction of an artificial snag that appears to be highly attractive to North American Chickadees, even those living in essentially unmanaged woodlands. Black-capped Chickadees and Carolina Chickadees are maximally attracted to cavity sites with the following attributes: (1) small diameter, possibly because of less competition for such sites from larger birds; (2) hard outer surface or "shells", presumably because such sites are more resistant to nest predators; and (3) considerable height above the ground presumably related to the finding that nest loss to predation is inversely correlated with height.

Gutierrez, R.J. 1993. Conservation Planning: Lessons from the Spotted Owl. U.S. For. Serv. Gen. Tech. Rep. RM No. 247 pp. 51-58.

Hagan, J.M. and S.L. Grove. 1995 report: selection cutting, old-growth, birds, and forest structure in Maine. Report MODCF-96002. Manomet Observatory for Conservation Sciences. Manomet, MA.

Hagan, J.M., W.M. Vander Haegen, and P.S. McKinley. 1996. The early development of forest fragmentation effects on birds. Conservation Biology 10(1): 188-202.

Early development of forest fragmentation effects on forest organisms is poorly understood partly because most fragmentation studies have been done in agricultural or suburban landscapes, long after the onset of fragmentation. The researchers develop a temporal model of forest fragmentation effects on densities of forest breeding birds and provide data from an active industrial forest landscape to test the model. The model and our empirical data indicate that densities of several forest-dwelling bird species can increase within a forest stand soon after the onset of fragmentation as a result of displaced individuals packing into remaining habitat. Thus density was inversely related to productivity. The duration and extent of increased densities following onset of fragmentation depends on many factors, including the sensitivity of a species to edge and area effects, the duration and rate of habitat loss and fragmentation, and the proximity of a forest stand to disturbance. Incipient forest fragmentation may affect populations differently from later stages of fragmentation when the geometry of the landscape has reached a more stable configuration. The researchers model and data indicate, for reasons unrelated to traditional edge effects, that large tracts of forest can be important because they are relatively free from the variety of plant and animal population dynamics that might take place near new edges, including the encroachment of individuals displaced by habitat loss.

Haig, S.M., J.R. Belthoff, and D.H. Allen. 1993. Population viability analysis for a small population of Red-cockaded
Woodpeckers and an evaluation of enhancement strategies. Conservation Biology 7(2): 289-301.

This study performed a series of population and pedigree analyses to examine the viability of a small Red-cockaded Woodpecker population located at the Savannah River Site in South Carolina. The population's existence and future survival are precarious. As few as four individuals, including just one breeding pair, comprised this population in 1985. Primarily because of experimental translocation, the population has increased to 25. Viability analyses indicated that, depending on relative effects of inbreeding depression and stochastic environmental events, the Savannah River Site population has a 68-100% chance of extinction in 200 years. Annual translocation into the population of at least three females and two males for a 10-year period will achieve a 96% probability of survival for 200 years. Even with translocation of numerous males and females per year (up to 50 of each), the 90% heterozygosity goal may not be achieved. The researchers discuss recommendations for choosing individuals for translocation, logistical constraints on achieving recovery objectives, and limitations of the modeling approach.

Hamer, T.E., E.D. Forsman, A.D. Fuchs, and M.L. Walters. 1994. Hybridization between Barred and Spotted Owls. Auk 111(2): 487-492.

Hansen, A.J., W.C. McComb, R. Vega, M.G. Raphael, and M. Hunter. 1995. Bird habitat relationships in natural and managed forests in the west cascades of Oregon. Ecol. Appl. 5(3): 555-569.

Hanula, J.L. and K.E. Franzreb. 1995. Arthropod prey of nestling Red-cockaded Woodpeckers in the upper coastal plain of South Carolina. Wilson Bull. 107(3): 485-495.

Four nest cavities of the Red-cockaded Woodpecker were monitored with automatic cameras to determine the prey selected to feed nestlings. Wood roaches made up 69.4% of the prey fed to nestlings. Other common prey items were wood borer larvae (5.4%), Lepidoptera larvae (4.5%), spiders (3.6%), and ants (3.1%). Wood roaches were the only prey items consistently taken by all four groups of birds; they made up 63.3% to 81.6% of the prey observed. Other common prey generally were taken in large numbers only by a single group of woodpeckers. During the breeding season these woodpeckers utilize relatively few common arthropods to feed nestlings.

Härdling, R., H. Källander, and J.A. Nilsson. 1997. Memory for hoarded food: An aviary study of the European Nuthatch. Condor 99: 526-529.

In an aviary study, each of six male European Nuthatches was allowed to hoard 30 sunflower seeds in natural hoarding substrates. The results suggest memory of cache sites.

Harper, R.G., S.A. Juliano, and C.F. Thompson. 1994. Intrapopulation variation in hatching synchrony in House Wrens: Test of the individual-optimization hypothesis. Auk 111(3): 516-524.

Intrapopulation variation in hatching synchrony has been documented in several avian species, although little attention has been paid to this phenomenon. This study experimentally reversed some synchronously hatched broods to test an individual-optimization hypothesis to explain variation in hatching synchrony in a population of House Wrens in central Illinois. Contrary to expectation, the number and quality (as measured by mass) of fledglings produced in reversed broods was the same as that for unmanipulated broods, as were recapture rates of juveniles and offspring recruitment to subsequent breeding populations. Although other adaptive hypothesis to explain such variation remain to be tested, we suggest that variation in hatching intervals may indicate that female control of hatching pattern is imprecise and may be unrelated to fitness in this House Wren population.

Harrison, S., A. Stahl, and D. Doak. 1993. Spatial models and Spotted Owls: Exploring some biological issues behind recent events. Conservation Biology 7(4):950-953.

Few species will ever challenge conservation biology as much as the Northern Spotted Owl has done. In this paper, the researchers describe the biological issues in this unusually science-rich legal debate. On present evidence, any plan entailing further loss of old-growth forest is incompatible with the legal mandate to ensure the owl's survival. In response, the Forest Service and its scientific supporters argue that the imminent collapse is not yet proven, and that the Thomas Strategy is a reasonable compromise between opposing interests. The researchers believe this case has highlighted a dangerous tendency among some conservation biologists to see political "realities" and compromise solutions as a paramount goal. Even if science is never value-free in practice, our aim in cases such as this should be to provide an accurate assessment of biological risks. Weighing these against other concerns and reaching compromises is the job of decision makers.

Hepp, G.R. and R.A. Kennamer. 1992. Characteristics and consequences of nest-site fidelity in Wood Ducks. Auk 109(4): 812-818.

This study used nine years of nesting data from a population of Wood Ducks using nest boxes to test predictions regarding proximate controls of nest-site fidelity and the consequences of returning to the same nest site. Overall, females nesting in the same box did not have greater nets success in year t + 1, were not more likely to have nests parasitized, and did not survive better to year t + 2 than females nesting in different boxes. However, females that nested unsuccessfully tended to improve nest success by moving to a different nest box.

Hernandez, A. 1995. Selective predation by northern shrikes on small mammals in a natural environment. J. Field Ornithol. 66(2): 236-246.

Hess, C.A. 1997. Stomach flushing: sampling the diet of Red-cockaded Woodpeckers. Wilson Bull. 109(3): 535-539.

Description of a non-destructive method to ascertain the diet of wild birds.

Hinsley, S.A., P.E. Bellamy, I. Newton, and T.H. Sparks. 1995. Habitat and landscape factors influencing the presence of individual breeding bird species in woodland fragments. Avian Biol. 26(2): 94-104.

Hinsley, S.A., P.E. Bellamy, and I. Newton. 1995. Bird species turnover and stochastic extinction in woodland fragments. Ecography 18: 41-50.

Year-to-year turnover in bird species composition was recorded across the whole size range (0.02 - 30 ha.) of 146 woods studied. The mean number of resident breeding species both lost and gained per wood between consecutive breeding seasons was 2 (range 0-8). No relationship was found between this absolute turnover rate and woodland area, or any other of 24 predictor variables. Extinction and colonization rates were also unrelated to woodland area. In all sizes of woods, the species most likely to show local extinctions and colonizations were those with small populations within those woods, but the identity of the species concerned changed as woodland area increased. In the smallest woods, the majority of turnover involved common species, such as wren and dunnock, which occurred in only small numbers. As woodland area increased, these species attained sufficient numbers to usually avoid stochastic extinction. The majority of turnover was then due to more specialist (and less numerous) species such as Great-spotted Woodpecker and Marsh Tit, which were usually lacking in small woods. In Britain, much existing broadleaved woodland falls within the size range studied. Thus the numbers of many bird species are liable to be small enough for yearly turnover in woodland bird communities to be appreciable, and for the long-term persistence of individual species in particular woods to depend on dispersal.

Hipes, D.L. and G.R. Hepp. 1993. Effect of mate removal on nest success of female Wood Ducks. Condor 95: 220-222.

Study tested whether removal of mates during egg-laying and early incubation influenced the nest success of female Wood Ducks at a southern breeding site. Hatching success and nest success of widowed and paired females were not different. Male Wood Ducks may remain with their mates for future reproductive opportunities. Extended pair bonds early in the breeding season would allow males to insure paternity of a second clutch in event of nest failures, or of a second nesting attempt. As the breeding season progresses, males may have less to gain by remaining with their mates and abandon them earlier in incubation as the season progresses. Further studies are needed to address the significance of male parental care in Wood Ducks.

Hipes, D.L. and G.R. Hepp. 1995. Nutrient-reserve dynamics of breeding male Wood Ducks. Condor 97: 451-460.

Hodges, M.F. and D.G. Krementz. 1996. Neotropical migratory breeding bird communities in riparian forests of different widths, along the Altamaha River, Georgia. Wilson Bull. 108(3): 496-506.

Survey of riparian forest corridors of different widths along the lower Altamaha River, Georgia in 1993 and 1994 to investigate the relationship between forest corridor width and Neotropical breeding bird community diversity and abundance. Species richness and abundance of three of six focal species increased with increasing forest corridor width. We suggest if Neotropical breeding bird communities are a target group, that land managers should consider leaving a 100 m buffer strip along riparian zones.

Horn, A.G. 1996. Dawn song repertoires of Tree Swallows (Tachycineta bicolor) Can. J. Zool. 74: 1084-1091.

Horn, A.G., M.L. Leonard, L. Ratcliffe, S.A. Shackleton, and R.G. Weisman. 1992. Frequency variation in songs of Black-capped Chickadees (Parus atricapillus). Auk 109(4): 847-852.

Hunter, J.E., R.J. Gutierrez, and A.B. Franklin. 1995. Habitat configurations around Spotted Owl sites in northwestern California. Condor 97(3): 684-693.

Ingold, D.J. 1994. Influence of nest-site competition between European Starlings and woodpeckers. Wilson Bull. 106(2): 227-241.

Study of nesting behaviour of 40 pairs of Red-bellied Woodpeckers, 42 pairs of Northern Flickers, and 23 pairs of Red-headed Woodpeckers during three breeding seasons 1990-92 in east-central Ohio. Red-bellied Woodpeckers incurred the brunt of starling competition for freshly excavated nest cavities and lost 39% of their cavities to Starlings. Flickers and Red-headed Woodpeckers were significantly more aggressive when defending their nest cavities. Woodpecker pairs not able to avoid starling competition may not have suffered reductions in fecundity since at least some of these pairs were able to re-nest successfully later in the season.

Johnson, L.S., M.S. Merkle and L.H. Kermott. 1992. Experimental evidence for importance of male parental care in monogamous House Wrens. Auk 109(3): 662-664.

Johnson, L.S. and R.M.R. Barclay. 1996. Effects of supplemental calcium on the reproductive output of a small passerine bird, the House Wren (Troglodytes aedon). Can. J. Zool. 74: 278-282.

Kallander, H., and J. Karlsson. 1993. Supplemented food and laying data in the European Starling. Condor 95: 1031-1034.

Karasov, W.H., M.C. Brittingham, and S.A. Temple. 1992. Daily energy and expenditure by Black-capped Chickadees (Parus atricapillus) in winter. Auk 109(2): 393-395.

Keller, M.E. and S.H. Anderson. 1992. Avian use of habitat configurations created by forest cutting in Southeastern Wyoming. Condor 94: 55-65.

Comparison of avian species composition and abundance in four pairs of sites, each pair having an uncut site and one fragmented by small clearcuts in southeast Wyoming. Fragmented stands were interrupted with strip or patch clearcuts. The abundance of species was also compared among the habitat configurations present on these sites such as forest interiors, meadow edges and clearcuts. Of 16 bird species, Brown Creepers and Hermit Thrushes were the most negatively influenced by fragmentation; Pine Siskins were the most positively influenced. The distribution of birds among forest interiors and edges suggested the responses to fragmentation were not generally mirrored by preferences or avoidance of forest edges and interiors. The effect of fragmentation may result from the loss of resources from clearcutting or preferences for the type of habitat adjacent to the forest stand (meadows or clearcuts).

Kennedy, E.D. and D.W. White. 1996. Interference competition for House Wrens as a factor in the decline of Bewick's Wrens. Conservation Biology 10(1): 281-284.

The researchers report on the impact of House Wrens on nesting failure of Bewick's Wrens and the results of experiments on egg-removal behaviour for Bewick's and House Wrens. The overwhelming source of nesting failure of Bewick's Wrens was nest vandalism by House Wrens. The researchers suggest that Bewick's Wrens represent the first documented case of a migratory species declining primarily because of interspecific competition.

Kirk, D.A., A.W. Diamond, A.R. Smith, G.E. Holland, and P. Chytyk. 1997. Population changes in boreal forest birds in Saskatchewan and Manitoba. Wilson Bull. 109(1): 1-27.

This study counted breeding birds at four plots in central Saskatchewan and four in western Manitoba in 1990-92 to examine changes since 1972-73. Trends in Saskatchewan may be representative of general declines within continuously forested boreal landscapes, whereas those in Manitoba may reflect reduced opportunities for breeding in continuous forest as the landscape is increasingly fragmented by agriculture.

Klatt, P.H. and G. Ritchison. 1993. The duetting behavior of Eastern Screech-Owls. Wilson Bull. 105(3): 483-489.

The bounce songs given by Screech-Owls during duets exhibit significant individual and sexual variation and may be used to advertise the presence and identify of a mated pair, confirm the identify of a mate, or determine the sex of a prospective mate.

Kleintjes, P.K. and D.L. Dahlsten. 1994. Foraging behavior and nestling diet of Chestnut-backed Chickadees in Monterey Pine. Condor 96: 647-653.

Study of the foraging behaviour and nestling diet of Chestnut-backed Chickadees during the breeding season in a Monterey Pine plantation 1991-92. Adults spent 79% of their foraging time on Monterey Pine as a result of prey availability. Nestling diet was composed of 43% Monterey Pine Sawfly larvae and 17% tree camel crickets. Spiders and other species comprised the remaining 40% of the diet. Monterey Pine serves as an important foraging resource for this species during the breeding season.

Koenig, W.D. and J.L. Dickinson. 1996. Nestling sex-ratio variation in Western Bluebirds. Auk 113(4): 902-910.

Tested five hypotheses for facultative manipulation of sex ratios in a population of Western Bluebirds studied for 13 years in California. The results urge caution when reporting sex-ratio biases in natural populations and when interpreting published studies, many of which suffer from small sample sizes, post hoc analyses, and insufficiently conservative statistical tests.

Kristan, D.M., R.J. Gutierrez and A.B. Franklin. 1996. Adaptive significance of growth patterns in juvenile Spotted Owls. Can. J. Zool. 74: 1882-1886.

This study examined relative growth patterns of six morphological features of fledgling Spotted Owls. Juvenile spotted owls exhibit early nest desertion, possibly to avoid parasitism or detection by predators or to reduce thermal stress. Because juveniles leave the nest before they are capable fliers, they primarily use features other than their wings and tails to move among roost locations. When juveniles fledged, mass, wing chord, and tail length were still increasing, whereas tarsus length and bill depth were near adult size. Moreover, juvenile bill length was greater than mean adult bill length for nearly all time periods. Early growth in tarsi and bills may increase juveniles' ability to effectively locomote after they have fledged but before they can adequately fly.

Kroodsma, D.E., D.J. Albano, P.W. Houlihan, and J.A. Wells. 1995. Song development by Black-capped Chickadees (Parus atricapillus) and Carolina Chickadees (P. Carolinensis). Auk 112(1): 29-43.

Labranche, M.S. and J.R. Walters. 1994. Patterns of mortality in nests of Red-cockaded Woodpeckers in the sandhills of southcentral North Carolina. Wilson Bull. 106(2): 258-271.

Lacombe, D., D.M. Bird, C.G. Scanes and K.A. Hibbard. 1993. The effect of restricted feeding on plasma growth hormone (GH) concentrations in growing American Kestrels. Condor 95: 559-567.

Lacombe, D., D.M. Bird and K.A. Hibbard. 1994. Influence of reduced food availability on growth of captive American Kestrels. Can. J. Zool. 72: 2084-2089.

LaHaye, W.S., R.J. Gutierrez, and D.R. Call. 1997. Nest-site selection and reproductive success of California Spotted Owls. Wilson Bull. 109(1): 42-51.

This study evaluated the quality of nesting habitat and nest-site selection of an insular population of California Spotted Owls. The results confirm previous observations that California Spotted Owls will use a variety of habitats, but these habitats are consistently characterized by greater structural complexity compared with available habitat.

Laidig, K.J. and D.S. Dobkin. 1995. Spatial overlap and habitat associations of Barred Owls and Great Horned Owls in southern New Jersey. J. Raptor Res. 29(3): 151-157.

Lamberson, R.H., R. McKelvey, B.R. Noon, and C. Voss. 1992. A dynamic analysis of Northern Spotted Owl viability in a fragmented forest landscape. Conservation Biology 6(4): 505-512.

Study reports on the results of a population model for the Northern Spotted Owl that incorporates both juvenile dispersal and search for mates. The researchers analyzed both deterministic and stochastic versions of the model in search of thresholds for population persistence related to search efficiency, population density, and amount of suitable habitat. In addition, they analyzed the model under the nonequilibrium conditions that currently exist due to timber harvest in the owls' preferred habitat. The results predict a sharp threshold below which populations cannot persist, and suggest that inferences from population models that incorporate equilibrium assumptions may be highly misleading.

Lamberson, R.H., B.R. Noon, C. Voss, and K.S. McKelvey. 1994. Reserve design for territorial species: The effects of patch size and spacing on the viability of the Northern Spotted Owl. Conservation Biology 8(1): 185-195.

Designing a reserve system for a threatened territorial species such as the Northern Spotted Owl requires the balancing of biological necessity against economic reality. The Spotted Owl conservation plan and the Pacific Northwest timber industry are in conflict because both demand large areas of mature and old-growth coniferous forests. This paper examined the relationship between the degree of aggregation of suitable owl habitat, the level of occupancy of that habitat by pairs of Spotted Owls, and the likelihood of owl persistence given different amounts and spatial arrangements of suitable habitat across the landscape. The researchers develop a population model for Spotted Owls that includes an abstracted forest landscape where suitable owl habitat is arrayed in clusters embedded in a matrix not suitable for owl habitation. The researchers conclude from their study of this model that, for any given fraction of the landscape set aside in reserves, the level of occupancy (efficiency of use) of that area will increase as the aggregation of suitable habitat increases. After the reserves reach a size that includes territories for 20 to 25 owl pairs, however, there are diminishing returns from further increases. Preserving connectivity and increasing the geographical extent of the reserve begin to outweigh increased size in importance in insuring the long-term viability of the species.

LaRue, P., L. Belanger and J. Huot. 1995. Riparian edge effects on boreal balsam fir bird communities. Can. J. For. Res. 25(4): 555-566.

Lawless, S.G., G. Ritchison, P.H. Klatt and D.F. Westneat. 1997. The mating strategies of Eastern Screech-owls: A genetic analysis. Condor 99: 213-217.

Use of genetic analysis to examine the mating strategies of male and female Eastern Screech-owls in central Kentucky. DNA fingerprinting revealed no evidence of extra-pair fertilizations in 23 broods (80 nestlings). Such results suggest that pursuit of extra-pair copulations by male and female Screech-owls may be costly. One possible cost for females is the risk of losing the nest site. Alternatively, pursuit of extra-pair matings by females might be energetically expensive, thereby conflicting with egg production. Male Screech-owls provide food for the mate (and young) during much of the breeding season and such feeding probably affects reproductive success. Males pursuing EPCs might have less time for foraging and, as a result, reduced reproductive success.

Lemmon, D., M.L. Withiamad, C.P.L. Barkan. 1997. Mate protection and winter pair-bonds in Black-capped Chickadees. Condor 99: 424-433.

Lent, R.A. and D.E. Capen. 1995. Effects of small-scale habitat disturbance on the ecology of breeding birds in a Vermont (USA) hardwood forest. Ecography 18: 97-108.

Study of territory placement and foraging behaviour of breeding birds in relation to juxtaposition of forest vegetation and logged patches in southern Vermont. Different bird species used disturbed vegetation at differing spatial scales. These analyses did not reveal any strong associations between foraging behaviour and use of cut versus uncut forest. Habitat use by birds occupying this forest mosaic, with its strong local gradient of vegetation structure, was thus not associated with concurrent variation in foraging behaviour. The sizes of cut patches of forest (0.7-1.6 ha) in the study area may be close to the minimum required to attract distinct breeding assemblages of non-forest birds to otherwise undisturbed forest ecosystems. Bird species that use patches of early-successional vegetation embedded in a forested landscape may adopt a fugitive strategy as they seek nesting habitats in the spring. Careful use of forest management techniques may permit both forest-interior and early-successional bird species to coexist in the landscape.

Levey, D.J. and W.H. Karasov. 1994. Gut passage of insects by European Starlings and comparison with other species. Auk 111(2): 478-481.

Ligon, J.D. and P.B. Stacey. 1996. Land use, lag times and the detection of demographic change: The case of the Acorn Woodpecker. Conservation Biology 10(3): 840-846.

Changes in land-use patterns that alter habitat may have a delayed negative effect on animal species occupying that habitat, and thus may not be recognized for years. This study examined a relatively stable population of the cooperatively breeding Acorn Woodpecker from 1975-84 in Water Canyon, New Mexico. These woodpeckers rely on self-constructed storage sites or "granary trees" to hold the acorns used during the winter and spring. Most granaries were in dead trunks and limbs of cottonwood trees. Storage sites form the primary basis for differential quality among territories. Groups of woodpeckers with large storage facilities (high-quality territories) have greater annual reproductive success and survival than do pairs or groups with poorly developed storage sites. In the summer of 1994 and 1995, the researchers censused the original study site, which had held 21 territories. Most territories which contained birds a decade earlier were unoccupied. This drastic decline was correlated with the loss of nearly all large storage facilities because of the collapse of the granary trees. Most neighbouring territories with lesser storage facilities also were vacant. The lack of production of new, high-quality granaries for the period 1975-1995 probably is due to the age structure of the cottonwood trees, which is distinctly bimodal; nearly all trees are either very young or old. The scarcity of middle-aged trees reflects a period of intensive cattle grazing in the area, during which production of young cottonwoods was suppressed.

Liknes, E.T. and D.L. Swanson. 1996. Seasonal variation in cold tolerance, basal metabolic rate, and maximal capacity for thermogenesis in White-breasted Nuthatches Sitta carolinensis and Downy Woodpeckers Picoides pubescens, two unrelated arboreal temperate residents. J. Avian Biol. 27: 279-288.

The researchers measured basal metabolic rate (BMR) and peak metabolic rate (PMR) for wild, free-living summer and winter acclimatized White-breasted Nuthatches and Downy Woodpeckers to determine seasonal and interspecific variations in cold tolerance and thermogenic ability. Woodpeckers and nuthatches exhibited roughly similar BMR and PMR at both seasons. Interspecific differences in cold tolerance and metabolic rates are probably explained, at least in part, by differences in body mass. These data indicate that White-breasted Nuthatches and Downy Woodpeckers exhibit similar thermogenic performance and major phylogenetic effects on thermoregulation are not apparent.

Lombardo, M.P. 1994. Nest architecture and reproductive performance in Tree Swallows (Tachycineta bicolor). Auk 111(4):814-824

Comparison of the architecture of nests built by subadult and adult female Tree Swallows in boxes in southeastern Michigan in order to determine if there were age-related differences in nest architecture and if these differences were associated with age-related differences in reproductive performance. There were age-related and within-season variations in reproductive performances associated with variations in nest architecture, especially later in the season. Among subadult females that bred later in the season, those females that built larger nests hatched more eggs per clutch. Among adult females that bred later in the season, those females that built nests that filled a lather percentage of the nest box hatched fewer eggs . Adult females with nests having larger cups produced significantly more fledglings, but those with cups crowded with nestlings produced significantly fewer fledglings. The results suggest that nestling hyperthermia in well-insulated nests may affect the reproductive performance of Tree Swallows that breed late in the season.

Lombardo, M.P., P.A. Thorpe, R. Cichewicz, M. Henshaw, C. Millard, C. Steen, and T.K. Zeller. 1996. Communities of cloacal bacteria in Tree Swallow families. Condor 98: 167-172.

Survey of the communities of bacteria found in the cloacae of adult and nestling Tree Swallows to determine if there were familial patterns of prevalence and to determine if there were relationships between bacteria loads and nestling size when 12 days old and fledging success.

Lozano, G.A. 1994. Size, condition, and territory ownership in male Tree Swallows (Tachycineta bicolor). Can. J. Zool. 72: 330-333.

Male Tree Swallow territory owners and floaters were compared in terms of size and nutritional condition to test the resource holding potential hypothesis. Owners were larger than floaters when compared using six morphological measurements. There were no differences in dry mass, ash, or fat content, but territory owners were heavier and had larger protein reserves than floaters. Territory owners may be those individuals who win intrasexual conflicts for the possession of nest boxes, or those who, because of their better nutritional condition, can arrive at the breeding grounds earlier to secure a territory.

Macdonald, D.W. and P.J. Johnson. 1995. The relationship between bird distributions and the botanical and structural characteristics of hedges. J. Appl. Ecol. 32(3): 492-505

Mallory, M.L. and P.J. Weatherhead. 1993. Observer effects on Common Goldeneye nest defense. Condor 95: 467-469.

Repeated visits to Common Goldeneye nests appear to affect nest defense. As incubation proceeded, female Common Goldeneyes exhibited stronger nest defense behaviour, supporting the prediction that nest defense should increase as young become more valuable. Although positive reinforcement is one reason birds might defend their nests more vigorously as a result of previous visits to the nest, another reason is that the birds might learn to recognize humans as more serious potential threats to their clutch. Female goldeneyes may learn to recognize humans as potentially more dangerous after seeing them climb the nest tree and open the box.

Mallory, M.L. and P.J. Weatherhead. 1993. Incubation rhythms and mass loss of Common Goldeneyes. Condor 95: 849-859.

Examination of incubation rhythms and mass loss of 16 female Common Goldeneyes. On average, female goldeneyes spent 81% of the day incubating eggs, and took 2.7 recesses per day, each lasting an average of 114 minutes. Females began incubation approximately 20% heavier than the lowest body mass they reached over the incubation period, a slightly greater mass loss than predicted for ducks their size. Female goldeneyes appeared to manage their mass loss by modifying their incubation behaviour. Females tended to lose less mass on days following more substantial mass loss, and once females approached their minimum mass they spent more time off the nest.

Maguire, L.A., G.F. Wilhere and Q. Dong. 1995. Population viability analysis for Red-cockaded Woodpeckers in the Georgia Piedmont. J. Wildl. Manage. 59(3): 533-542.

Matthysen, E., F. Adriaensen and A.A. Dhondt. 1995. Dispersal distances of nuthatches, Sitta europaea, in a highly fragmented forest habitat. Oikos 72: 375-381

Study of the dispersal distances of nuthatches in a highly fragmented landscape with only 2% of its area covered by suitable habitat (mature forest and parkland). It was estimated that most surviving nestlings settled outside the 200 km2 study area, and that mean dispersal distance was several times larger compared to more densely forested landscapes. However, local recruitment did not differ between this study and other studies in large forests. Once young nuthatches had settled, they were less likely to move again in the fragmented landscape compared to large forests. We conclude that fragmentation causes an increase in natal dispersal distance but no discernible change in the number of territories between birth and establishment. However, fragmentation does effectively include isolation once the young birds have settled.

Matthysen, E. and D. Currie. 1996. Habitat fragmentation reduces disperser success in juvenile Nuthatches Sitta europaea: Evidence from patterns of territory establishment. Ecography 19: 67-72.

Study of the establishment of summer territories by first-year Nuthatches Sitta europaea both in a large forest and in a set of small and isolated forest fragments (2 yr in each area). In the large forest, vacant territories were rapidly taken up by newly formed pairs of juveniles. In the fragments, settlers arrived at a slower rate, more of them remained unpaired, and more territories remained vacant at the end of the dispersal period. Furthermore, territories were taken up in a highly predictable order related to territory quality in the large forest, but not so in the fragments. We suggest that dispersal is more costly in a highly fragmented habitat, reducing the number of settlers at the population level, and reducing opportunities for pair formation and habitat selection at the individual level.

McCallum, D.A., F.R. Gehlbach and S.W. Webb. 1995. Life history and ecology of Flammulated Owls in a marginal New Mexico population. Wilson Bull. 107(3): 530-537.

Study of Flammulated Owls nesting in a forest-woodland ecotone at the species' lower elevation limit. Most adults did not re-nest in the same tree cavity despite previous success. Our study population is marginal ecologically, perhaps limited by food shortage during courtship plus predation and maintained immigration.

McCarty, J.P. 1997. Aquatic community characteristics influencing the foraging patterns of Tree Swallows. Condor 99: 210-213.

Collection of emerging insects from experimental ponds indicated that nutrient additives and the removal of fish greatly increased the number of insects emerging from these ponds. The ability of Tree Swallows to exploit local concentrations of food may be critical to their ability to return to the breeding grounds before aerial insects are reliably available.

McIntyre, N.E. 1995. Effects of forest patch size on avian diversity. Landscape Ecol. 10(2): 85-99.

Mikusinski, G. 1995. Population trends in Black Woodpecker in relation to changes and characteristics of European forests. Ecography 18: 363-369.

During the last century, the Black Woodpecker has expanded its range in central and western Europe. Habitat changes were the most common explanations of these expansions. This study compared changes in forest characteristics in countries where different Black Woodpecker population trends were observed. Results showed that countries with positive population trends had significantly higher increase in coniferous forest volume. These countries had also significantly higher proportion of young forest stands. The importance of coniferous forests, as well as importance of forest structure of the Black Woodpecker, are discussed.

Mitchell, J.S. and R.J. Robertson. 1996. Extra nest site occupancy by Tree Swallows: Do floaters avoid nest sites near settled pairs? Wilson Bull. 108(4): 797-802.

Tested the hypothesis that extra nest site occupancy by Tree Swallows results from avoidance by floaters of nest sites near settled pairs.

Moller, A.P. 1994. Facts and artifacts in nest-box studies: Implications for studies of birds of prey. J. Raptor Res. 28(3): 143-148.

Morrell, T.E. and R.H. Yahner. 1994. Habitat characteristics of Great Horned Owls in southcentral Pennsylvania. J. Raptor Res. 28(3): 164-170.

Murray, N.L. and D.F. Stauffer. 1995. Nongame bird use of habitat in central Appalachian riparian forests. J. Wildl. Manage. 59: 78-88.

Nakamura, M., Y. Suzuki, and Y. Masatoshi. 1995. Artificial wooden boxes for roosting woodpeckers. Wildl. Soc. Bull. 23(1): 78-79

The researchers describe the development of a bottomless roosting box for woodpeckers. The idea was derived from observing behaviour of woodpecker species that roosted in an empty trunk of a tree with several entrances. The advantage of this type of box for woodpeckers are: 1) the boxes are always available because other birds can't use them for breeding or roosting; 2) if a woodpecker in this box is attacked by predators such as snakes or cats, the woodpecker can escape easily through the other exit. Moreover, the researchers could easily and safely verify use of the box by woodpeckers from the bottom of the boxes by flashlight. The species found using the boxes included Great Spotted Woodpecker, Japanese Green Woodpecker and Pygmy Woodpecker.

Neal, J.C., D.A. James, W.G. Montague, and J.E. Johnson. 1993. Effects of weather and helpers on survival of nestling Red-cockaded Woodpeckers. Wilson Bull. 105(4): 666-673

Non-breeding adult Red-cockaded Woodpeckers, termed helpers, participate in many aspects of the nesting cycle, including feeding nestlings. Typically, groups that include helpers exhibit a higher nesting success and fledge more young than groups lacking helpers. This study examined Red-cockaded Woodpeckers in the Ouachita National Forest in Arkansas in 1991-92. In both years, woodpecker groups with helpers suffered fewer losses and fledged more young per nesting attempt (P<0.001).

Negro, J.J., A. Chastin and D.M. Bird. 1994. Effects of short-term food deprivation on growth of hand- reared American Kestrels. Condor 96: 749-760.

Sudden prey reductions were simulated to examine their impact on growth of American Kestrels hand-reared in captivity. No long-term effects caused by temporary starvation were noted. Although starved individuals suffered a significant weight loss following the periods of food deprivation, they recovered mass in 2-4 days by increasing food ingestion. This flexibility of the growth of mass can be seen as an adaptive mechanism to permit compensation in day to day fluctuations of the food supply.

Newton, I. 1994. The role of nest sites in limiting the numbers of hole-nesting birds: a review. Biol. Conserv. 70(3): 265-276

Nickens, E. 1995. Is forest management harming songbirds? Am. For. 101(9): 18-21, 41-42.

O'Connor, T.P. and T.L. Root. 1993. Effects of handling time and freezing on catabolic enzyme activity in House Sparrow pectoralis muscle. Auk 110(1): 150-152.

Ohlsson, T. and H.G. Smith. 1994. Development and maintenance of nestling size hierarchies in the European Starling. Wilson Bull. 106(3): 448-455.

Otter, K., L. Ratcliffe and P.T. Boag. 1994. Extra-pair paternity in the Black-capped Chickadee. Condor 96: 218-222.

Female Black-capped Chickadees may be engaging in a mixed reproductive strategy of social monogamy while increasing reproductive success by extra-pair copulations with males of higher genetic quality than their own mate. Females may also benefit from engaging in EPCs with dominant males if, by doing so, this facilitates rapid pair bonding with the dominant male in the event that his mate dies. The study documents rates of extra-pair paternity in an Ontario population of Black-capped Chickadees, using DNA fingerprinting. The results suggest that female chickadees might be engaging in a mixed reproductive strategy.

Pardieck, K.L., J.M. Meyers, and M. Pagan. 1996. Surveys of Puerto Rican Screech-Owl populations in large-tract and fragmented forest habitats. Wilson Bull. 108(4): 776-782.

Road surveys were conducted of Puerto Rican Screech-Owls by playing conspecific vocalizations in secondary wet forest and fragmented secondary moist forest in rural areas of eastern Puerto Rico. Six paired surveys were conducted bi-weekly beginning in April. Owls responded in similar numbers (P>0.05) in both habitat types. No correlation was detected of the number of owls with cloud cover, wind speed, moon phase, or passing cars.

Parvosudov, V.V. 1993. Breeding biology of the Eurasian Nuthatch in Northeastern Siberia. Wilson Bull. 105(3): 475-482.

Paton, P.W. 1994. The effect of edge on avian nest success: How strong is the evidence? Conservation Biology 8(1): 17-26.

A current dogma is that edges adversely affect a wide range of avian species by increasing depredation and parasitism rates of nests. The researcher critically evaluated existing empirical evidence to test whether there was a gradation in nest success as a function of distance from an edge. Researchers investigating this question have been inconsistent in their experimental designs, making generalizations about edge-effect patterns difficult. The majority of studies the researcher examined found nest success varied near edges, with both depredation rates (10 of 14 artificial nest studies and 4 of 7 natural nest studies) and parasitism rates (3 of 5 studies) increasing near edges. In addition, there was a positive relationship between nest success and patch size (8 of 8 studies). The most conclusive studies suggest that edge effects usually occur within 50 m of an edge, whereas studies proposing that increased depredation rates extend farther than 50 m from an edge are less convincing. Prior research has probably focused on distances too far from an edge to detect threshold values, and future research should emphasize smaller scales: 100-200 m from an edge at 20-25 m increments. Researchers often use relatively arbitrary habitat characteristics to define an edge. Therefore, the researcher proposes that only openings in the forest canopy with a diameter three times or more the height of the adjacent trees should be included in edge analyses. The review suggests that fragmentation of eastern North American temperate forests could lead to increased nest predation and parasitism, and there is need to determine if similar processes occur in other forested regions of North America.

Pelech, S., and S.J. Hannon. 1995. Impact of tent caterpillar defoliation on the reproductive success of Black-capped Chickadees. Condor 97: 1071-1074.

Investigation of the effects of forest tent caterpillar outbreaks on the reproductive success of Black-capped Chickadees near Athabasca, Alberta. The study tested two predictions: (1) in years with tent caterpillar outbreaks, initiation of breeding would be earlier and clutch sizes larger in response to extra food when compared to years with no outbreaks; (2) tent caterpillar defoliation would reduce the reproductive success and subsequent survival of female chickadees through limitation during brood-rearing. The study concluded that tent caterpillar outbreaks did not influence the earliest breeding parameters (date of clutch initiation, clutch size) and may not have represented a significant increase to the food supply of chickadees. When defoliation was at its peak, some pairs had reduced reproductive success in the form of complete or partial loss of the brood to starvation.

Petty, S.J., G. Shaw and D.I.K. Anderson. 1994. Value of nest boxes for population studies and conservation of owls in coniferous forests in Britain. J. Raptor Res. 28(3): 134-142.

Pinxten, R., M.Eens, and R.F. Verheyen. 1994. Communal breeding in the European Starling: Evidence from DNA fingerprinting. Auk 111(2): 482-486.

Plissner, J.H. and P.A. Gowaty. 1995. Eastern Bluebirds are attracted to two-box sites. Wilson Bull. 107(2): 289-295.

In early March, just prior to the onset of the breeding season, responses by Eastern Bluebirds to playbacks of the territorial song of conspecifics are more likely on sites with two-nest boxes rather than one. Explanations include that bluebirds prefer potential territorial sites with two boxes because of increased habitat quality or that bluebirds locate two-box sites more readily than one-box sites. We infer that potential territorial sites with two nesting boxes are more attractive to bluebirds then sites with only one nesting box.

Pochop, P.A., R.J. Johnson and K.M. Eskridge. 1993. House sparrow response to monofilament lines at nest boxes and adjacent feeding sites. Wilson Bull. 105(3): 504-513.

Previous studies show that House Sparrows are repelled from feeding sites by monofilament lines spaced 30 or 60 cm apart. Lines may repel House Sparrows from feeding areas because of predation risk and need for rapid escape but not from nest sites, which are selected in secure locations.

Pogue, D.W. and G.D. Schnell. 1994. Habitat characteristics of secondary cavity-nesting birds in Oklahoma. Wilson Bull. 106(2): 203-226.

Analysis of vegetation structure at potential and actual nest sites of secondary cavity-nesting birds in south-central Oklahoma. Habitats consisted of old fields with remnants of tallgrass prairie and patches of post oak-blackjack oak woodland. 194 sites with nest boxes were analyzed during the 1989 and 1990 breeding seasons. Use of principal-components analysis to describe vegetation gradients and stepwise discriminant analysis to delineate differences in nest-site habitats among species was employed.

Pogue, D.W. and W.A. Carter. 1995. Breeding biology of secondary cavity-nesting birds in Oklahoma. Southwest Nat. 40(2): 167-173.

Potti, J. 1993. Environmental, ontogenetic, and genetic variation in egg size of Pied Flycatchers. Can. J. Zool. 71: 1534-1542.

Quinn, M.S. and G.L. Holroyd. 1992. Asynchronous polygyny in the House Wren (Troglodytes aedon). Auk 109(1): 192-195.

Redpath, S.M. 1995. Habitat fragmentation and the individual: Tawny Owls Strix aluco in woodland patches. J. Animal Ecol. 64: 652-661.

Examination of Tawny Owls in continuous and fragmented woodland habitats to determine the effect of fragmentation on behaviour, breeding success and turnover. Information on home range and territorial behaviour was obtained from 23 radio-tagged individuals. In the fragmented woodland area Tawny Owl home ranges contained more woodland than expected from random. Within home ranges, usage of habitat was such that woodland > buildings > grassland > arable areas. Owls utilized the grassland and arable areas by hunting from the ground. In continuous woodland, owl home ranges overlapped more and they were more often involved in territorial behaviour than those in fragmented woodland. It is concluded that the intermediate woods, where food is abundant and energetic costs are not great, present an optimum habitat for Tawny Owls in this area. The study indicates that data on breeding success and turnover are essential in determining the effects of habitat fragmentation and that these effects may not be easy to predict, given information from non-fragmented areas.

Redpath, S.M. and I. Wyllie. 1994. Traps for capturing territorial owls. J. Raptor Res. 28(2): 115-117.

Reed, J.M., J.R. Walters, T.E. Emigh, and D.E. Seaman. 1993. Effective population size in Red-cockaded Woodpeckers: Population and model differences. Conservation Biology 7(2): 302-308.

Loss of genetic variability in isolated populations is an important issue for conservation biology. Most studies involve only a single population of a given species and a single method of estimating rate of loss. This study presents analyses for three different Red-cockaded Woodpecker populations from different geographic regions. The reseachers compared two different models for estimating the expected rate of loss of genetic variability, and tested their sensitivity to model parameters. It was found that the simpler model consistently estimated a greater rate of loss of genetic variability from a population than did the other. For Red-cockaded Woodpeckers, estimates of effective size were extremely sensitive to survival parameters, but not to the probability of breeding or reproductive success. Sensitivity was sufficient that error in estimating survival rates in the field could easily mask true population differences in effective size. The results indicate that accurate and precise demographic data are prerequisites to determining effective population size for this species using genetic models, and that a single estimate of rate of loss of genetic variability is not valid across populations.

Reed, J.M. and J.R. Walters. 1996. Helper effects on variance components of fitness in the cooperatively breeding Red-cockaded Woodpecker. Auk 113(3): 608-616.

Examined the effects helpers have on variance in reproductive success and breeder survival in Red-cockaded Woodpecker. It was found that helpers did not affect variance in breeder survival, but variance in reproductive success was affected by helpers at nests that produced young. Like helper effects on mean reproductive success, helper effects on variance in reproductive success might be confounded by effects of habitat quality.

Rendell, W.B. 1992. Peculiar behavior of a subadult female Tree Swallow. Wilson Bull. 104(4): 756-759.

Rendell, W.B. 1993. Intraspecific killing observed in Tree Swallows, Tachycineta bicolor. Canadian Field-Naturalist 107(2): 227-228.

Description of an incident of intraspecific killing (by drowning), and two other possible cases of killings, by Tree Swallows at a nest-box population in British Columbia. The observations leave no doubt that fights between Tree Swallows may lead to intraspecific killing in this species, and they are discussed in light of the unusually limited availability of nest-sites in the study area in 1991.

Rendell, W.B. and N.A.M. Verbeek. 1996. Old nest material in nest boxes of Tree Swallows: effects on nest-site choice and nest building. Auk 113(2): 319-328.

The accumulation of old nest material might affect nest-site selection and nest building by hole-nesting birds. This study tested this hypothesis by manipulating the presence and amount of old nest material in nest boxes of Tree Swallows. The experiment also allowed the researchers to examine whether costs are incurred by females due to nest building in terms of their subsequent reproductive output. When choice of boxes was available, swallows preferred empty and clean boxes, or those where the old material had been microwaved, over those with old, untouched material. Clean boxes and those with microwaved material had more space inside, so the experiments supported two hypothesis: swallows avoid potentially high numbers of parasites in nests with old material; or they prefer large cavities. The results show that the common habit of removing old nests from boxes can affect nest-site choice and nest-building behaviour. Nest building does not influence reproductive output by Tree Swallows.

Rendell, W.B. and N.M. Verbeek. 1996. Old nest material in nestboxes of Tree Swallows: Effects on reproductive success. Condor 98: 142-152.

Renken, R.B. and E.P. Wiggers. 1993. Habitat characteristics related to Pileated Woodpecker densities in Missouri. Wilson Bull. 105(1):77-83.

Examination of relationships among Pileated Woodpecker densities and forest habitat characteristics on 16 study areas in Missouri during 1985-86. Pileated Woodpecker abundance ranged from 0.5 to 4.1 territories/100 ha. Regression analysis indicated a positive, linear relationship between Pileated Woodpecker abundance and percent of an area covered with bottomland forest, density of trees >= 30 cm dbh, and density of snags >= 54 cm dbh. Percent of area covered with pole timber (>15 cm and < 25 cm dbh) was negatively related to Pileated Woodpecker abundance. Study areas with greater amounts of bottomland forest (>= 4.5%, N=7) had a higher density of snags >= 54 cm dbh (P=0.005) and smaller amounts of pole timber cover (P=0.04) than study areas with < 4.5% bottomland forest cover (N=9). The findings indicated that large trees and huge snags are important features in Pileated Woodpecker habitat, and these features were most often associated with bottomland forest.

Rich, A.C., D.S. Dobkin, and L.J. Niles. 1994. Defining forest fragmentation by corridor width: The influence of narrow forest-dividing corridors on forest-nesting birds in southern New Jersey. Conservation Biology 8(4): 1109-1121.

In studies of forest fragmentation, a fundamental inconsistency exists in the distance criterion used to define the discreteness of forest fragments. We examined three types of ubiquitous, narrow, forest-dividing corridors for effects that influence the relative abundance and community composition of forest-nesting birds. Fixed-radius (100 m) point counts were conducted on 54 transects established along three width classes of corridors: unpaved roads (8 m wide), paved roads (16 m wide), and powerlines (23 m wide). Transect locations were distributed equally among corridor edge, forest margin 100 m from corridor edge, forest interior 300 meters from corridor edge. Forest-interior species of Neotropical migrants had significantly reduced relative abundances on edge transects along 16- and 23-meter corridors, compared with 8-meter corridors and with forest interior points along all three corridor-width classes. At a landscape scale, the consequences of apparently small reductions in forest area by the presence of narrow forest-dividing corridors may be cumulatively significant for abundances of forest interior species. The researchers suggest that these widespread corridors may be inconspicuous but important contributors to declines of forest-interior nesting species in eastern North America.

Richardson, D.M. and D.L. Smith 1992. Hardwood removal in Red-cockaded Woodpecker colonies using a shear V-blade. Wildl. Soc. Bull. 20(4): 428-433.

Shearing has been widely used in the forest industry as a site-preparation method primarily for pine planting. This technique has potential for removing hardwoods from Red-cockaded Woodpecker colonies because stem density and tree size do not affect shearing operations. The researchers' objective was to evaluate the use if a shear V-blade to remove extensive hardwood encroachment in active and inactive Red-cockaded Woodpecker colonies in east-central Mississippi.

Richardson, M. and R.W. Knapton. 1993. Regional use, selection, and nesting success of Wood Ducks, Aix sponsa, using nest boxes in Ontario. Canadian Field-Naturalist 107(3): 293-304.

Duck nesting-box surveys in 1990 and 1991 in Ontario on the use of nest boxes by Wood Ducks and other species provided information on 1,808 nest boxes, of which 1,678 were analyzed. There were 510 reported nesting attempts by Wood Ducks of which 303 were successful, 87 unsuccessful and 106 unknown. Nest box use showed strong regional variation; lowest in northern Ontario, highest in the Sudbury area and eastern Ontario. Density of breeding Wood Duck populations and availability of suitable nesting cavities probably explain this variation. Nest boxes placed in swamps and around sewage lagoons had the highest occupancy rates. Nest boxes placed about 2.5 m above ground, highly visible and with a clear flight path to the nest hole were preferred over higher or more concealed boxes. Nest-box distance to water did not affect occupancy or nesting success. Nest boxes with smaller entrance holes were occupied more than those with larger holes; average area of entrance hole of occupied boxes was 63 cm2. Clumped boxes were used less than expected, but had higher nesting success.

Robb, J.R. and T.A. Bookhout. 1995. Factors influencing Wood Duck use of natural cavities. J. Wildl. Manage. 59(2): 372-383.

Roby, D.D., K.L. Brink, and K. Wittmann. 1992. Effects of Bird Blowfly parasitism on Eastern Bluebird and Tree Swallow nestlings. Wilson Bull. 104(4): 630-643.

Large numbers of Bird Blowfly larvae in nests reportedly cause nestling morbidity and mortality in some host species, but other studies have failed to find significant effects. This study conducted controlled blowfly removal and addition experiments to reveal the effects of blowfly infestations on nestling growth, development, and survival of Eastern Bluebirds and Tree Swallows. Blowflies were found in about 70% of the nests of both species. The effects of blowfly parasitism on reproductive success were minor and apparently exerted little selection pressure for nest dispersion in the two study species.

Rohrbaugh, R.W. and R.H. Yahner. 1997. Effects of macrohabitat and microhabitat on nest-box use and nesting success of American Kestrels. Wilson Bull. 109(3):410-423.

A study of nesting ecology of American Kestrels in Pennsylvania from 1987-91. Kestrels used 76% of 130 nest boxes dispersed throughout a 1,000 km2 study area. Of all nesting attempts, 49% successfully fledged at least one offspring. Five macrohabitat and 14 microhabitat variables were measured at the 130 nest boxes. Ten variables were correlated to levels of nest box use and nesting success. Kestrels most frequently used nest boxes with high nestling-light intensity and low nest-box concealment. Frequently used boxes were associated with extremely open habitat dominated by herbaceous vegetation (P<0.005). Nesting Kestrels avoided using boxes associated with dense habitats, such as late-successional old fields. Frequently used nest boxes were farther from forested areas than unused boxes (P=0.05). Nest boxes with southeast orientations were used more frequently than expected (P<0.025) and all other orientations were used in proportion to availability. Kestrels had the greatest nesting success when using nest boxes with high selection-light intensities (P=0.05).

Rooneem, T.M. and R.J. Robertson. 1997. The potential to lay replacement clutches by Tree Swallows. Condor 99: 228-231.

To determine the factors that influence a female's decision of whether or not to re-lay, the researchers removed first clutches from 17 marked female Tree Swallows in a nest-box population in eastern Ontario. Females and nests were then monitored to determine whether a replacement clutch was laid. Forty-one percent of females laid replacement clutches. First clutches of those females that laid replacement clutches were significantly larger than those of females that did not re-lay. This suggests that female quality, indicated by having higher levels of expendable energy or greater foraging skill or efficiency, is the determining factor as to whether or not a replacement clutch will be laid. For birds that re-laid, the replacement clutch was significantly smaller than the first clutch. This suggests either a depletion of ebergy reserves with each subsequent nesting attempt, or an individual female's energetic tradeoffs to ensure her own survival to the nest breeding season.

Rosenfield, R.N., J. Bielefeldt, J.L. Affeldt and D. J. Beckmann. 1995. Nesting density, nest area reoccupancy, and monitoring implications for Cooper's Hawk in Wisconsin. J. Raptor Res. 29(1): 1-4.

Rudolph, D.C., R.N. Conner, D.K. Carrie, and R.R. Schaefer. 1992. Experimental reintroduction of Red-cockaded Woodpeckers. Auk 109(4): 914-916.

A major void in management procedures is the current lack of a technique to artificially establish woodpecker groups and populations de novo. Previous efforts to relocate Red-cockaded Woodpecker breeding pairs met with limited success. The recent improvement in cavity-construction techniques and experience in translocating individual birds convinced us that it was time to revisit the issue. Standard translocation techniques were employed and modified. In the case of reintroductions to vacant habitat, we strongly support the use of simultaneous multiple reintroductions. The simultaneous reintroduction of 5-10 pairs in a spatial array dense enough to permit social contact of adjacent pairs could immediately result in the establishment of at least a partially functioning population.

Rudolph, D.C. and R.N. Conner. 1993. Forest fragmentation and Red-cockaded Woodpecker population: an analysis at intermediate scale. J. Field Ornithol. 65(3): 365-375.

Rytkönen, S. and M. Soppela. 1995. Vicinity of Sparrowhawk nest affects Willow Tit nest defense. Condor 97: 1074-1078.
Sedgwick, J.A. 1997. Sequential cavity use in a cottonwood bottomland. Condor 99: 880-887.

Study of the patterns and frequency of cavity reuse in a community of cavity-nesting birds in a cottonwood bottomland along the South Platte River in northeastern Colorado from 1985-87. Of 100 cavities occupied in 1985, 56% we reused in 1986; 38.5% of 122 cavities occupied in 1986 were reused in 1987. Of 81 old cavities monitored in both 1986 and 1987, 65.4% were reused at least once. Similar proportions of secondary cavity-nesting bird (SCNB) and primary cavity-nesting bird (PCNB) cavities were reused in both years. Reoccupancy by the same species was 27% and 20.5% in 1986 and 1987, respectively, and was greater for SCNB than for PCNB cavities in both years. Conversely, reoccupancy by different species was greater for PCNB than for SCNB cavities in both years. Thus, old cavities of PCNB were more available to other species of cavity-nesting birds, whereas old SCNB cavities tended to be reused by the same species that previously occupied the cavity. SCNB used a greater proportion of old cavities than did PCNB in both 1986 and 1987. House Wrens and Northern Flickers reoccupied most of the old cavities.

Semel, B. and P.W. Sherman. 1995. Alternative placement strategies for Wood Duck nest boxes. Wildl. Soc. Bull. 23(3): 463-471.

The researchers compared two ways of positioning nest boxes for Wood Ducks. In one area in northeast Illinois, pairs of boxes were erected on posts over water. In an adjacent area, boxes were mounted singly on trees in deciduous woodlands. Traditionally placed boxes (visible duplexes) were parasitized more often than non-traditionally placed (hidden, dispersed) boxes (72% vs. 35%; P < 0.001) and received more parasitic eggs/clutch. Over four years, parasitism rates nearly tripled among traditionally placed boxes but remained low among non-traditionally placed boxes despite similar box use (87% vs. 84%, respectively). The results show (1) a clear relationship between nest box placement and frequency of brood parasitism, (2) rarity of unoccupied boxes does not determine rate of parasitism, and (3) extreme brood parasitism reduces reproductive efficiency. The researchers suggest that if nest boxes are distributed in inconspicuous sites, local Wood Duck populations will more likely achieve their full reproductive potential.

Shackleton, S.A., L. Ratcliffe, and D.M. Weary. 1992. Relative frequency parameters and song recognition in Black-capped Chickadees. Condor 94: 782-785.

Shackleton, S.A. and L. Ratcliffe. 1993. Development of song in hand-reared Black-capped Chickadees. Wilson Bull. 105(4): 637-644.

Hand rearing of pairs of nestlings in acoustic isolation to determine the extent that learning is involved. Results suggest that the structure of Black-capped Chickadee song is open to environmental influences and that chickadees may learn the relative frequency parameters of their song.

Shepherd, D. 1992. Monitoring Ontario's owl populations: a recommendation. Long Point Bird Observatory. Port Rowan, Ontario.

Sherman, D.E., R.M. Kaminski, and B.D. Leopold. 1992. Potential indices of Mallard and Wood Duck abundance in forested wetlands during winter. Wildl. Soc. Bull. 20(2): 148-156.

The goal of this research was to evaluate the potential utility of flying-duck counts at dusk and aerial surveys as independent indices of Mallard and Wood Duck abundance in forested wetlands during winter.

Sherman, D.E., R.M.Kaminski, and B.D. Leopold. 1995. Winter line-transect surveys of Wood Ducks and Mallards in Mississippi greentree reservoirs. Wildl. Soc. Bull. 23(2): 155-163.

An evaluation of line-transect sampling from the ground and estimation of densities of wintering Wood Ducks and Mallards in three greentree reservoirs in Mississippi. The researchers also compared density estimates from the programs TRANSECT II and SIZETRAN, and tested the relationship between seasonal abundances of ducks and selected environmental variables.

Siders, M.S. and P.L. Kennedy. 1996. Forest structural characteristics of accipiter nesting habitat: Is there an allometric relationship? Condor 98: 123-132.

In montane forests of the western U.S., a general correlation of accipiter body size and scaling of the vegetation component of nesting sites and nest trees used by sympatric Accipiter species has been reported. This study evaluated this pattern with data collected at Northern Goshawk, Cooper's Hawk and Sharp-shinned Hawk nest sites in New Mexico. We selected habitat variables at the nest tree and nest site scale that would allow us to evaluate the prediction that accipiters use nesting habitat in which their body size if positively correlated with tree size and tree spacing, and inversely correlated with tree density, basal area, and percent canopy closure. The results suggest there is a correlation between accipiter size and nest tree size, but that a correlation between nest size structural size and accipiter body size may not be a widespread phenomena for all vegetation variables for all three species.

Simberloff, D. 1993. How forest fragmentation hurts species and what to do about it. U.S. For. Serv. Gen. Tech. Rep. RM No. 247. pp. 85-90.

Sintich, S.M., M.K. Keagle, R.G. Harper, and I.G. Welsford. 1995. Use of Elisa for determination of plasma prolactin levels in the House Wren. Condor 97: 1057-1061.

Smith, H.G. and T. Von Schantz. 1993. Extra-pair paternity in the European Starling: The effect of polygyny. Condor 95: 1006-1015.

Determination of the frequency of extra-pair paternity and intraspecific brood parasitism in European Starlings by performing multilocus DNA fingerprinting on 22 complete families from a population in southern Sweden.

Sproat, T.M. and G. Ritchison. 1993. The nest defense behavior of Eastern Screech-owls: Effects of nest stage, sex, nest-type and predator location. Condor 95: 288-296.

The responses of male and female Eastern Screech-owls to a human approaching the nest were examined. Intensity of nest defense was more pronounced during the nestling stage than during the incubation stage. These results generally support both the age-investment and positive-reinforcement hypothesis. Male owls defended nestlings more vigorously than females. The increased maneuverability of the smaller males may have contributed to this difference. Males also responded with greater intensity as the human intruder moved closer to the nest; such a response informs the potential predator of the direction it must move to reduce the likelihood of injury.

Sproat, T. M. and G. Ritchison. 1994. The antipredator vocalizations of adult eastern Screech-Owls. J. Raptor Res. 28(2): 93-99.

Squires, J.R. and L.F. Ruggiero. 1995. Winter movements of adult Northern Goshawks that nested in southcentral Wyoming. J. Raptor Res. 29(1):5-9.

Stangel, P.W., M.R. Lennartz, M.H. Smith. 1992. Genetic variation and population structure of Red-cockaded Woodpeckers. Conservation Biology 6(2): 283-292.

This study surveyed genetic variability and examined population structure in the endangered Red-cockaded Woodpecker, a species whose distribution has been fragmented by land-use patterns. Sixteen presumptive gene loci were resolved from feather pulp of nestlings and adults from 26 populations rangewide. Genetic distance among populations increased with geographic distance. Although heterozygosity is reduced in some small populations, most exhibit "normal" levels. Small populations should therefore not be considered "lost causes" from the genetic standpoint. Small populations are important as reservoirs of unique genetic combinations and help facilitate gene flow among larger populations.

St. Louis, V.L., and J.C. Barlow. 1993. The reproductive success of Tree Swallows nesting near experimentally acidified lakes in northwestern Ontario. Can. J. Zool. 71: 1090-1097.

The study found that near acidified lakes, eggs were smaller in certain dimensions, hatching success was lower (and by definition fewer nestlings fledged per nest box), certain nestling body characteristics were smaller four days posthatch, nestling wing length was shorter near time of fledging, and growth functions were different from those near unmanipulated reference lakes. The results are consistent with earlier findings that calcium-rich food items needed for egg production by laying females and growth of nestlings are more scarce at acidified lakes than at nonacidic reference lakes, and that potentially toxic metals accumulate to higher concentrations both in the chironomids that swallows consume and in nestling swallows at acidified lakes. Our results clearly show that even nonaquatic organisms are affected by acidification of freshwater ecosystems.

Swengel, S.R. and A.B. Swengel. 1992. Roosts of Northern Saw-whet Owls in southern Wisconsin. Condor 94: 699-706.

Descriptions of 623 roosts of Northern Saw-whet Owls in southern Wisconsin from 1986-90. Roosts were in seven species of trees with 97.9% in White and Norway spruces, red and jack pines and eastern red cedar. Mean roost height was 4.05 ± 2.21m in a 9.15 ± 3.40 m tall tree. Roosts averaged 46.6 ± 43.4 cm from the trunk on a 150.4 ± 69.6 cm long limb. Roost characteristics varied according to tree species, size, and shape. Mean roost height ranged from 1.5 ± 0.4 m in eastern red cedars to 6.9 ± 1.3 m in red pines. Roost height correlated positively with tree height and negatively with distance of roost from trunk. Distance of roost from trunk correlated positively with limb length. Directions of roosts relative to the trunk were random. Mean roost height and height of roost tree increased with time. Most roosts afforded good cover from above and most sides. Saw-whet Owls chose roosts that provided concealment, not those of a particular height. Roosts conferred thermal benefits on owls. Behaviour of roosting Saw-whet Owls suggests that the owls' motionlessness when approached by humans is a camouflaging strategy.

Taylor, B.L. and T. Gerrodette. 1993. The uses of statistical power in conservation biology: The Vaquita and Northern Spotted Owl. Conservation Biology 7(3): 489-500.

The consequences of accepting a false null hypothesis can be acute in conservation biology because endangered populations leave little margin for recovery from incorrect management decisions. The concept of statistical power provides a method of estimating the probability of accepting a false null hypothesis. The researchers illustrate how to calculate and interpret statistical power in a conservation context with two examples based on the Vaquita, an endangered porpoise, and the Northern Spotted Owl. For the Northern Spotted Owl, estimates of power allow a reinterpretation of results of a pervious demographic analysis that concluded the population was stable. The researcher found that even if the owl population had been declining at 4% per year, the probability of detecting the decline was at most 0.64, and probably closer to 0.13; hence, concluding that the population was stable was not justified. Calculations of power can also be used to compare different methods of monitoring changes in the size of small populations. The optimal method of monitoring Northern Spotted Owl populations may depend both on the size of the study area in relation to the effort expended and on the density of animals.

|Teather, K. 1996. Patterns of growth and asymmetry in nestling Tree Swallows. J. Avian Biol. 27: 302-310.

Growth rates of three bilateral characters of nestling Tree Sparrows were monitored to (a) determine the suitability of these characters in assessing fluctuating asymmetry and (b) test the hypothesis that fluctuating asymmetry of any or all of these characters is correlated with other growth parameters that may be indicative of genetic and/or environmental stress.

Telleria, J.L. and T. Santos. 1995. Effects of forest fragmentation on a guild of wintering passerines: the role of habitat selection. Biol. Conserv. 71: 61-67.

Thomlinson, J.R. 1995. Landscape characteristics associated with active and abandoned Red-cockaded Woodpecker clusters in East Texas. Wilson Bull. 107(4): 603-614.

Investigation of spatial characteristics of Red-cockaded Woodpecker cluster size in the Sam Houston National Forest, Texas. Active cluster sites were larger and closer to other active clusters than inactive ones and had larger gravity interaction values. Inactive sites were significantly more isolated than were active clusters, they were more likely to be surrounded by inimical land uses, and they were less likely to be connected by corridors of mature timber to active cluster sites. This research indicates that spatial landscape parameters influence Red-cockaded Woodpecker cluster status and they should be considered in management plans for the species.

Thompson, F.R. 1993. Simulated responses of a forest-interior bird population to forest management options in central hardwood forests of the United States. Conservation Biology 7(2): 325-333.

The researcher used estimates of carrying capacity, survival, fecundity, and edge effects to simulate the responses of a forest-interior bird population to selection cutting, clearcutting, and no timber harvest. The study also modeled population sensitivity to changes in fecundity, survival, K, and edge relationships. Simulated population size was greater with no timber harvest than with clearcutting, and greater with clearcutting than with group selection when edge effects were included in the model. Without edge effects, population levels were only slightly lower under group selection than under no timber harvest, and greater than clearcutting. Edge effects had only a small impact on population levels under clearcutting. Clearcut size did not have much effect on population levels, but longer and shorter rotation ages resulted in higher and lower population levels, respectively. The model was very sensitive to declines in mean fecundity and survival, suggesting that factors affecting mean demographic rates could be more important than local edge effects. Some methods of timber harvest may be compatible with the conservation of forest-interior birds, but better demographic data and information on habitat suitability of selectively cut forests and young even-aged stands is needed to adequately evaluate management options.

Tobalske, B.W. 1992. Evaluating habitat suitability using relative abundance and fledging success of Red-naped Sapsuckers.
Condor 94: 550-553.

Examination of the relative abundance of Red-naped Sapsuckers in unlogged and recently logged coniferous forest. This effort was augmented with an analysis of fledging success to determine whether such modified habitats provide suitable nesting opportunities for this species. As the relative abundance of Red-naped Sapsuckers and the number of young fledged per nest did not differ significantly between logged and unlogged stands forest management guidelines that require snag and live tree retention within cutting units provided useful nest sites for this species. Although Red-naped Sapsuckers nested successfully in logged areas, unlogged coniferous forest surrounding the cutting units was probably essential to adult survival and productivity.

Tobalske, B.W. 1996. Scaling of muscle composition, wing morphology, and intermittent flight behavior in woodpeckers. Auk 113(1): 151-177.

Examination of the relationships between functional morphology and intermittent flight behaviour within a closely-related group of birds using six species of woodpeckers: Downy Woodpecker, Red-naped Sapsucker, Hairy Woodpecker, Lewis' Woodpecker, Northern Flicker, and Pileated Woodpecker.


Torres, A.R. and P.L. Leberg. 1996. Initial changes in habitat and abundance of cavity-nesting birds and the Northern Parula following Hurricane Andrew. Condor 98: 483-490

Examination of the initial effects of Hurricane Andrew on nest site availability and abundance of seven species of cavity-nesting birds and the Northern Parula in a large bottomland hardwood forest associated with the Atchafalaya River in Louisiana. None of the abundances of the individual cavity-nesting species were related to hurricane damage or the availability of cavities. Northern Parula abundance was negatively correlated with hurricane damage and density of understory vegetation. The low abundance of this species in forests heavily damaged by the hurricane may be due to loss of canopy foraging habitat or of Spanish Moss, one of its principal nesting sites.

Townsend Peterson, A., N. Ingle, and R. Fernandez. 1995. Notes on the nesting behavior of the White-bellied Woodpecker. Wilson Bull. 107(1): 182-184.

Varland, D.E. and T.M. Loughin. 1993. Reproductive success of American Kestrels nesting along an interstate highway in Central Iowa. Wilson Bull. 105(3): 465-474.

Study of the reproductive success of Kestrels nesting in nest boxes attached to the backs of highway signs along Interstate 35 in central Iowa, 1988-92. Nest box occupancy averaged 45.1%. All nest boxes faced either north or south and there was no significant association between nest box occupancy and nest box orientation. European Starlings built nests in almost every nest box not occupied by Kestrels. The percentage of nests fledging at least one young averaged 68.9%. There was no significant associated between apparent nesting success and nest box orientation. Using the Mayfield method, a significantly lower probability of survival during the incubation stage was detected than during the brood-rearing stage. Clutch size averaged 4.8 over the five years and mean hatching success was 62.5%. Mean brood size was 3.1 and mean number of young in a brood to fledge was 2.9. The Kestrels in this study had reproductive success similar to that of Kestrels nesting in nest boxes in other areas of North America.

Vierling, K.T. 1997. Habitat selection of Lewis' Woodpeckers in Southeastern Colorado. Wilson Bull. 109(1): 121-130.

Villard, P. 1994. Foraging behavior of Black-backed and Three-toed Woodpeckers during spring and summer in a Canadian boreal forest. Can. J. Zool. 72: 1957-1959.

During one spring to summer study in a Canadian boreal forest, Black-backed Woodpeckers were found to excavate mainly on logs and at the base of large-diameter tree trunks. In contrast, Three-toed Woodpeckers preferred higher strata and smaller diameter trunks. The predominant foraging technique used by Three-toed Woodpeckers was bark scaling. Canadian Three-toed Woodpeckers showed foraging behaviour similar to that found in European Woodpeckers, but in the Nearctic range they have not fully developed the sap-licking behaviour that is typical of the Three-toed Woodpeckers of the Western Palearctic range.

Virkkala, R., A. Rajasarkka, R.A. Vaisanen, M. Vickholm, and E. Virolainen. 1994. The significance of protected areas for the land birds of southern Finland. Conservation Biology 8(2): 532-544.

The value of protected areas in preserving land birds in Finland was studied on the basis of quantitative censuses. The number of bird pairs were estimated in nature reserves and in the whole of southern Finland, and the significance of the reserves was evaluated based on how large a proportion of the total population in southern Finland was found in them. Forest habitat generalists and species of coniferous forests occurred in protected areas as expected by the proportion of these areas in southern Finland. Species of old-growth forest and open peatlands clearly preferred protected areas, whereas species of bushes, and lush and deciduous forests were scarcer in protected areas than elsewhere in southern Finland. The latter fertile habitats are poorly represented in protected areas, even though due to their disappearance or alteration elsewhere several species confined to these habitats have declined and are even threatened. Drainage of open peatlands and clearcutting of old-growth forests has caused a decrease in the area of these habitats in southern Finland during the past decades. Therefore protected areas have a high significance in preserving bird species preferring these habitats. Protected areas are particularly important for decreased species of old-growth forests, such as the Three-toed Woodpecker and the Siberian Jay, as about 10% of their total population in southern Finland was estimated to breed in protected areas. The future protection of both old-growth and deciduous forests is important if we are to preserve biodiversity of land birds in Finland.

Wagner, R.H., P. Davidar, M.D. Schug, and E.S. Morton. 1997. Do blood parasites affect paternity, provisioning and mate-guarding in Purple Martins? Condor 99: 520-523.

Wallraff, H.G., J. Kiepenheuer, M.F. Neumann, and A. Strong. 1995. Homing experiments with Starlings deprived of the sense of smell. Condor 97: 20-26.

Three hundred and forty European Starlings were caught in nest boxes in southern Germany. Half were made anosmic by bilateral olfactory nerve section, the others were sham operated and served as controls. The birds were displaced over distances of 30, 60, 120 and 240 km. Over 30 and 60 km, both controls and anosmic starlings returned at a rate of 40-50%. Over the longer distances, the return rate of controls remained the same (120 km) and decreased only slightly (240 km) whereas the percentage of anosmic homers was drastically and significantly reduced. The findings are analogous to corresponding results obtained with homing pigeons and strongly suggest that starlings also require perception of olfactory signals for orientation to home over longer distances. Returnings to the nest site in the following spring was also significantly lowered by anosmia, suggesting that olfactory navigation is involved in seasonal migration.

Walters, J.R., C.K. Copeyon, and J.H. Carter. 1992. Test of the ecological basis of cooperative breeding in Red-cockaded Woodpeckers. Auk 109(1): 90-97.

The researchers hypothesized that cavities excavated in living pines, because they require much time to construct, are the critical determinant of habitat quality that has led to cooperative breeding in Red-cockaded Woodpeckers. These woodpeckers rarely colonize sites that lack existing cavities. To test the hypothesis, cavities were drilled in 20 unoccupied sites. Eighteen were occupied subsequently, but none of the 20 control sites were used. These results support the contention that variation in habitat quality dependent on the presence or absence of cavities is the ecological basis of group formation in Red-cockaded Woodpeckers. Cavity construction may be used to increase the number of groups in a population, and to prevent territory abandonment when bird-constructed cavities are lost.

Wasser, S.K., K. Bevis, G. King and E. Hanson. 1997. Noninvasive physiological measures of disturbance in the Northern Spotted Owl. Conservation Biology 11(4): 1019-1022.

The Northern Spotted Owl continues to decline across its entire range at a rate exceeding 4% per year, with a 1% annual acceleration. One possible factor impeding its recovery is the lack of adequate measures that reflect the impact of habitat disturbance on this species. The researchers demonstrate that noninvasive hormone measurements of physiological stress in feces could provide an objective, readily accessible and cost effective means of quantifying impacts of disturbance in Northern Spotted Owls that can directly address pivotal conservation questions surrounding this and other listed species. Fecal stress hormone disturbance measures can be used as a proactive management tool, enabling the industry and wildlife managers to optimize the tradeoffs between resource utilization and proliferation of species at risk.

Wayland, M. and D.K. McNicol. 1994. Movements and survival of Common Goldeneye broods near Sudbury, Ontario, Canada. Can. J. Zool. 72: 1252-1259.

Wesolowski, T. 1995. The loss of avian cavities by injury compartmentalization in a primeval European forest. Condor 97: 256-257.

Examination of the loss of avian cavities due to injury compartmentalization in the Bialowieza National Park in Poland.

White, D.W. and E.D. Kennedy. 1997. Effect of egg covering and habitat on nest destruction by House Wrens. Condor 99: 873-879.

To test if eggs were protected by covering, prelaying wrens were challenged for one day with a set of two boxes placed one metre from their nest, one with two artificial eggs lightly covered under fur, and the other with two artificial eggs in an open cup. Boxes in woodland interiors were less likely than boxes in fields and along edges to be visisted by wrens at least once every two days and were less likely to have eggs removed. Competitors for nesting cavities may alkso escape attacks by wrens through differences in breeding period, active defense of territories or nests, or renesting.

Whitehead, S.C., J. Wright, and P.A. Cotton. 1996. Measuring the impact of parental foraging by Starlings (Sturnus vulgaris) on soil invertebrate prey availability: an exclosure experiment. Oikos 76: 511-521.

Depletion of soil invertebrate availabilities by starling foraging during the breeding season was investigated by using exclosures to create areas where the birds could not feed. A field 'preferred' by the wild birds was compared with a 'non-preferred' field. Prey biomass was measured from soil cores and the foraging success of individuals feeding in experimental exclosures gave a measure of prey availability. Foraging by these birds resulted in significant short-term depletion after a few hours of foraging. Comparison with exclosure sites at the end of the chick-feeding period showed that foraging by the wild birds caused significant long-term depletion. This depletion was greatest in the 'preferred' field, which offered a higher availability of leatherjackets, Tipula paludosa. These findings suggest that soil core analysis alone is insufficient to predict the foraging success of starlings and other birds feeding on soil invertebrates. The significant reduction in prey availability to parent starlings is discussed in relation to the number of parental foraging trips made to the two fields.

Wiebe, K.L. and G.R. Bortolotti. 1994. Energetic efficiency of reproduction: the benefits of asynchronous hatching for American Kestrels. J. Animal Ecol. 63: 551-560.

In 1989-91, the researchers used electronic event recorders at 57 nestboxes to record the number of visits Kestrels made to experimentally synchronous and asynchronous broods during the nestling period. In another experiment, the prey provisioning by parents to broods supplemented with food was recorded. Nestlings were weighed every third day until fledging. Synchronous broods require more energy to rear than asynchronous broods with the same number of young. This is consistent with the sibling rivalry hypothesis, but not with the peak load hypothesis. The extra energetic cost of synchronous broods may be exacerbated when food is scarce.

Wiebe, K.L. 1996. The insurance-egg hypothesis and extra reproductive value of last-laid eggs in clutches of American Kestrels. Auk 113(1): 258-261

Wiebe, K.L. and G.R. Bortolotti. 1996. The proximate effects of food supply on intraclutch egg-size variation in American Kestrels. Can J. Zool. 74: 118-124

The researchers measured eggs from 275 clutches of wild American Kestrels to study the degree of intra-clutch variability in egg size. They also performed two food-supplementation experiments to investigate the proximate role of food supply during egg laying in determining egg size. Females with relatively abundant food and those in good body condition did not lay eggs that were more uniform in size than those laid by control females. This result is contrary to the hypotheses that propose an adaptive explanation for intraclutch egg size variation and also to ideas of energy depletion during laying. Patterns of egg-size vs. laying order were different between years, suggesting that females did not adaptively manipulate laying order and egg size within a clutch. The food supplementation experiments showed that laying female kestrels probably depend on both stored energy reserves and on daily energy surpluses to form eggs. It appears that slight intraclucth variations in egg size occur in response to short-term food shortages during laying, but that these variations are probably nonadaptive. This is in marked contrast to interclutch (among females) variation in egg size, which the researchers have shown varies significantly with food supply.

Wiehn, J. 1997. Plumage characteristics as an indicator of male parental quality in the American Kestrel. J. Avian Biol. 28: 47-55.

Wiggins, D.A. and T. Part. 1995. Sexual dimorphism and breeding success in Tree Swallows and collared flycatchers. Condor 97: 267-271.

Willson, M.F., T.L. De Santo, C. Sabag, and J.J. Armesto. 1994. Avian communities of fragmented south-temperate rainforests in Chile. Conservation Biology 8(2): 508-520.

The diversity and relative abundance of south-temperate rainforest birds decreased as the size of the habitat patch decreased. Ecological categories, including endemics, mutualists (pollinators, seed dispersers), understory species, and species dependent on large trees, were not differentially sensitive to patch size. Nevertheless, most of the species with at least marginally significant declines were endemic (6 of 7 species), covered nesters (6 of 7 species) and understory dwellers (5 of 7 species). Some mutualists and big-tree users were also affected. The losses will become more severe as clearing of the forest continues. Possible mitigation measures include leaving small stands of forest and corridors between habitat patches and, in certain circumstances, alternative agricultural practices.

Wilson, S.F. and N.A.M. Verbeek. 1995. Patterns of Wood Duck nest temperatures during egg-laying and incubation. Condor 97: 963-969.

Study of the thermal environment of Wood Duck nests in southeastern British Columbia. Mean daily nest temperatures (Tn) were correlated with maximum daily air temperatures. Tn increased as the egg-laying period advanced among both successful and unsuccessful nests, although Tn was lower among unsuccessful nests. Length of the incubation period was not correlated with clutch size, nor with mean overall nest temperatures during incubation, but was correlated with the variance of Tn's during incubation.

Winkler, D.W. 1992. Causes and consequences of variation in parental defense behavior by Tree Swallows. Condor 94: 502-520.

Experimental study of parental defense behaviour in Tree Swallows using ferrets and rat snakes. Males defended more
aggressively than females. This may be a correlate of stronger territorial behaviour in this sex, rather then a strategic response to differing relatedness to the brood. Ferrets were defended against more strongly than were snakes. This may be a response to greater efficacy of defense behaviour against ferrets. The observations suggest that defense has three functions in Tree Swallows: 1) intimidation if small nest-site competitors; 2) moving on; and 3) distraction of larger nest predators.

Winkler, D.W. 1993. Use and importance of feathers as nest lining in Tree Swallows (Tachycineta bicolor). Auk 110(1): 29-36.

Tree swallows commonly line their grass nests with feathers of other species. In one of the years studied, there was a significant negative correlation between numbers of feathers in the nests and chick nestling periods (i.e. broods surrounded by more feathers fledged earlier). Feather removal experiments were conducted on some of the nests. It is suggested that feathers aid chicks directly by preventing hypothermia and indirectly through higher growth rates by allowing earlier fledging when necessary. Protection from ecoparasites may be an important advantage in natural nests where nest cavities are not cleaned out annually. Inadvertent removal of feathers from nest boxes may be an important cause of posthatching declines in feather numbers.

Winkler, D.W. 1995. Effects of handicapping on female condition and reproduction in Tree Swallows (Tachycineta bicolor). Auk 112(3): 737-747.

Yahner, R.H. 1993. Effects of long-term forest clear-cutting on wintering and breeding birds. Wilson Bull. 105(2): 239-255.

Study examined the effects of even-aged clear-cutting (third cutting cycle) on wintering and breeding bird communities in central Pennsylvania, 1987-89. Tested the hypothesis that community structure and population abundance of wintering and breeding birds did not differ (1) among areas that varied in extent of clear-cutting (0%, 50% and 75%) or (2) among habitats of different age since clear-cutting on the treated sector (50% and 75% areas). These findings were compared to those obtained subsequent to a second cutting cycle. It was concluded that the creation of a mosaic of small (1 ha.), even-aged stands for management of Ruffed Grouse habitat does not have a detrimental long-term effect on most species of breeding and wintering forest birds on a localized basis.

Yom-Tov, Y. and A. Ar. 1993. Incubation and fledging durations of woodpeckers. Condor 95: 282-287.

The relatively long fledging duration of cavity-nesting birds has been related to the relative safety of their nesting sites. This study compared the relationships between body and egg masses and incubation and fledging times of 39 species of woodpeckers and wrynecks to those of altricial birds in general. It was found that Picidae have shorter incubation and longer fledging periods in the comparable range of altricial birds' body and egg masses. However, total development duration is similar to that of other altricial birds. It is suggested that the short incubation of Picidae is an adaptation to the apparently poor gas exchange parent in the nest chamber, where oxygen and carbon dioxide levels may be low and high, respectively, and early transition to pulmonary respiration associated with an increase in nest ventilation is of advantage.

Young, B.E. 1994. Geographic and seasonal patterns of clutch-size variation in House Wrens. Auk 111(3): 545-555.

Young, B.E. 1994. The effects of food, nest predation and weather on the timing of breeding in tropical House Wrens. Condor 96: 341-353.

Tested three hypothesis that could explain variation in the timing of breeding in populations of House Wrens at four sites in Costa Rica. The first hypothesis was that breeding is timed to coincide with peaks in food availability. The second hypothesis was that breeding is timed to avoid seasons when nest predation is high. The third hypothesis was that breeding is timed to avoid climatic events that can increase the physiological costs of reproduction in tropical House Wrens seems generally to be timed to facilitate post-breeding activities, not activities associated with nesting itself.

Zabel, C.J., K. McKelvey and J.P. Ward Jr. 1995. Influence of primary prey on home-range size and habitat use patterns of Northern Spotted Owl (Strix occidentalis caurina). Can. J. Zool. 73: 433-439

Correlations between the home-range size of Northern Spotted Owls and the proportion of their range in old-growth forest have been reported, but there are few data on the relationship between their home-range size and prey. The primary prey of Spotted Owls are wood rats and northern flying squirrels. The study presents data indicating that the home ranges of spotted owls are smaller where their diet consists predominantly of wood rats than where it consists predominantly of flying squirrels, and the proportion of the diet consisting of wood rats and flying squirrels explained significant variation in home-range size. The study also found a significant correlation between home-range size and abundance of wood rats. These data indicate that prey species are a better predictor of home-range size than the proportion of older forest within spotted owl home ranges in the Klamath Province of northwest California and southwest Oregon, an area which is predominantly late-successional forest. Differences in habitat use were also related to prey species. Where spotted owls foraged for wood rats, the results indicated a preference for habitat edges, but where they utilized flying squirrels no such patterns were apparent.

Zicus, M.C. 1997. Female Hooded Merganser body mass during nesting. Condor 99: 220-224.

Body mass of female Hooded Mergansers nesting in widely dispersed and newly erected wooded nest boxes in northcentral Minnesota was measured in 1982-85. There was no indication that females having the greatest body mass began nesting earliest. However, females with the greatest body mass incubated the largest clutches and hatched the most young. Comparison of the observed body mass-clutch size relationship with one assumed to exist in the absence of interspecific brood parasitism indicated that more parasitic eggs were laid in nests incubated by heavier females.

Zicus, M.C. and S.K. Hennes. 1993. Diurnal time budgets of breeding Common Goldeneyes. Wilson Bull. 105(4): 680-685.

Studies of time allocation during nesting allow comparison of how waterfowl cope with energetic and nutrient demands within environmental constraints. Female goldeneyes are cavity-nesters. Early nesting suggests that stored resources are important, but foraging defense and low laying rates indicate foods obtained in the breeding areas may be essential.

Zicus, M.C. and S.K. Hennes. 1995. Common Goldeneye nest attendance patterns. Condor 97: 461-472.

Ziolkowski, D.J., Jr., L.S. Johnson, K.M. Hannam, and W.A. Searcy. 1997. Coordination of female nest attentiveness with male song output in the cavity-nesting House Wren Troglodytes aedon. J. Avian Biol 28: 9-14.

During the incubation stage of breeding, male House Wrens periodically move very near nest cavities and sing, and females, who alone incubate in this species, often appear to wait to take a break from incubating until they hear their mate singing nearby. Females may benefit from waiting to exit nests until their mates are singing nearby because: (1) the male's song indicates to the female that no predators are present, (2) males will be present to guard nests, especially against conspecifics, in the female's absence, and/or (3) males can act as sentinels while females are foraging.

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