Cape St. Marys is located on the southwestern tip of the Avalon Peninsula at the entrance to Placentia Bay. The cliffs along the mainland rise to approximately 130 m above sea level, with grassy barrens being present on top. An isolated sea stack (Bird Rock) is located offshore. Colonial seabirds nest along approximately 4 km of mainland cliff and on the isolated stack. The site extends east and southwards out of the ecological reserve to include : Bull Island Point, the small islets of Bull, Cow and Calf islets, St. Marys Keys (Cays), and Lance Point.
Cape St. Marys supports a large colony of breeding seabirds. In all, over 30,000 breeding pairs are present. Common Murres and Black-legged Kittiwakes are the most abundant with their populations being conservatively estimated in the late 1980s at approximately 10,000 pairs each. This represents approximately 2% of the eastern North America population of Common Murres and 4 to 5% of the western Atlantic breeding population of Black-legged Kittiwakes. A large population of Northern Gannets is also present with breeding populations being estimated in the late 1980s at 5,485 pairs. This represents approximately 2% of the global population and as much as 12% of the North American population. Other seabirds nesting at Cape St. Marys include Thick-billed Murres, Razorbills, Black Guillemots, Herring Gulls, Great Black-backed Gulls, Great Cormorants, and Double-crested Cormorants.
The Cape St. Marys area also supports large numbers of migrant seaducks (Oldsquaw, scoters, eiders), including large numbers of the eastern population of Harlequin Ducks (nationally endangered). About 30 to 40 birds are reported in some years. This may be greater than 1% of the eastern North America population of Harlequin Duck.
Conservation responses/actions for key biodiversity
In 1983, the main breeding colony and some adjacent ocean at Cape St. Marys was established as a Provincial Ecological Reserve under the Wilderness and Ecological Reserves Act. The reserve is a popular tourist attraction and draws many tens of thousands of visitors each summer. During the summer months, it is staffed by provincial naturalists.
Historically, gannet populations were severely reduced by direct human predation and more recently by the accumulation of toxic chemicals. Oil pollution, both chronic and catastrophic is also a concern, especially considering that the colony is located near a major shipping route from the Hibernia oilfields to refineries and oil storage facilities in Placenta Bay. There is also a high level of shipping traffic in the area, especially in winter.
A number of seabird studies and surveys have been conducted by researchers from Memorial University of Newfoundland and the Canadian Wildlife Service.
BirdLife International (2023) Important Bird Areas factsheet: Cape St. Mary's. Downloaded from
http://www.birdlife.org on 01/04/2023.