State of the Greater Fundy Ecosystem - Winter distribution of loons

GREATER FUNDY ECOSYSTEM RESEARCH PROJECT

UNB Faculty of Forestry and Environmental Management

State of the Greater Fundy Ecosystem

Winter Distribution of the Common Loon and the Red-throated Loon in the Bay of Fundy

Heather Clay and Douglas Clay
Fundy National Park, P.O. Box 40,
Alma, N.B., E0A 1B0

Loons are considered an indicator of 'wilderness quality' in northern freshwater lakes in Canada and the northeastern United States. The objective of this study was to determine if the presence of the newly established loons at Wolfe Lake in Fundy National Park (Fundy NP) was due to an increasing population in eastern North America or the reduced recreational use of Wolfe Lake. The study examined the distribution of the birds in the Greater Fundy Ecosystem (GFE). The greater park ecosystem for the Common Loons in Fundy NP was seen as including the Bay of Fundy (Figure 1).

Information on loon biology, distribution and behavior for Fundy NP and the GFE has been assembled over the years from Fundy NP Bird Sighting Cards (BSC) and Christmas Bird Counts (CBC). BSCs were completed by volunteers and park staff between 1948 and 1980. These records mostly contain information about the Park area and the adjacent coastal zone. CBC data has been collected by many volunteers over a 35 year period at 5 or more sites on both sides of the Bay of Fundy (Figure 1). The CBC is believed to provide a true indication of trends in the loon populations.

Common Loons and Red-throated Loons are known to over-winter along both the Atlantic and Pacific coasts once they leave their summer breeding sites on inland lakes. BSC records show that Common Loons continually use the coastal waters adjacent to Fundy NP from April to early November. Red-throated Loons breed in the Arctic and have never been observed away from the coast in the local area. They are most frequently seen in autumn and winter. Their large occurrences along the coast in late April probably indicates that they are staging for their migration north.

During April-May, Common loons use the coastal waters off Fundy NP as a staging area before moving to inland lakes to nest. Unsuccessful nesting by loons on interior lakes causes them to leave the lakes at the end of July to early August and to form off-shore groups. The birds leave the Fundy NP coastal areas as temperatures drop in late autumn. Red-throated Loons, being an Arctic species, tend to remain along the coast until mid-January.

The CBC data indicate an increase in overwinter Common Loon numbers along the New Brunswick coast of the Bay of Fundy. Along the Nova Scotia shore, Common Loon numbers appear more stable. CBC data for Red-throated Loon show no evident trend for this species in the Bay of Fundy. Overwinter populations appear to be low and highly variable. They also appear to be more uniformly distributed throughout the bay than the Common Loon during the December/January early winter period. Like the Common Loon, the Red-throated Loon also appears to occur in greater numbers along the New Brunswick rather than the Nova Scotia shore of the Bay of Fundy.

The increase in Common Loon overwintering numbers on the north shore of the bay may explain why the birds are seeking and establishing nesting sites within Fundy NP. Protected areas are important for loons because human interference (recreation) and unstable environments can result in nesting failure. Reducing human recreational-use impacts on lakes suitable for loon nesting within the Park may lead to an expansion of loon summer range on other park lakes.

Common Loon mortality during the marine overwintering period can have a significant effect on the populations of this species in seeming unrelated areas. During this time, the loon molts (loses its feathers) and cannot easily move from location to location in search of food. The loon's lack of mobility increases its risk of starvation if the fish populations in the area have moved or been removed through overfishing. The loons are also particularly at risk from contamination by sea borne pollutants during the winter molt (Spitzer, 1995). The Red-throated Loon may be susceptible to the same types of stresses although its molting period is in the autumn (Godfrey, 1979).

Loon numbers and distribution in the Bay of Fundy may be influenced by several recent trends. Since the early 1980's an aquaculture industry has developed in many sheltered coastal areas. Wild fish attracted to aquaculture cages may be increasing the availability of food for fish-eating birds. As well, there has been a reduction in fish processing plant effluent in coastal areas since the late 1970s. However, natural variations in marine fish populations are great and likely overshadow any changes due to scavenging.

Further reading:

Clay, H. and D. Clay. n.d. Winter distribution of the Common Loon (Gavia immer) and Red-throated Loon (Gavia stellata) in the Bay of Fundy. Unpublished paper on file at Fundy National Park. Alma, N.B.

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