Portnova Island is located about 13 km southeast of the town of Louisbourg, which is on the eastern coast of Cape Breton Island, Nova Scotia. The IBA also includes Chameau Rock, which is smaller and just a few kilometres north of Portnova, roughly midway to Cape Breton (the actual cape). This collection of islands, islets and reefs is rocky and treeless. They are ice-bound only in the spring when onshore winds blow ice flows in from the Gulf of St. Lawrence. These islands and islets experience typical damp and foggy Maritime weather with snow rarely lying on the ground for long. The tidal range is approximately 3 - 4 m.
The majority (> 70%) of the North American population of Great Cormorants is found in Nova Scotia. The most recent estimates suggest that there are a little over 6,000 birds in Canada, making the colony on Portnova Island (approximately 2.5% the North American population) highly significant. The results of earlier studies indicate that there were as many as 507 birds in 1971, but in 1992, there were only 310 on Portnova Island.
Although Great Cormorants often breed inland in Europe and Asia, they are strictly coastal breeders in North America. Cormorants prefer nest sites that are within commuting range of adequate food resources and safe from terrestrial predators. As a result, isolated islands, and steep rocky cliffs that are within commuting range of adequate food resources, are favoured as nesting sites.
BirdLife International (2022) Important Bird Areas factsheet: Portnova Islands. Downloaded from http://www.birdlife.org on 14/08/2022.