Corossol Island

Country/territory: Canada

IBA Criteria met: A4i (2008)
For more information about IBA criteria please click here

Area: 1,700 ha

Birds Canada / Nature Canada

Site description
Île du Corossol is located 10 km off the north shore of the Gulf of St. Lawrence, in the bay of Sept-Iles, Québec. Corossol Island is one of several islands in the Sept-Iles Archipelago. The IBA site includes the islets, rocks and water within a 500 metre limit around the island, except in the vicinity of Manowin Island where the limit is midway between the two islands. The island is overall rocky and steep, with three intermittent streams and, being part of the Canadian shield, is underlain by granitic-gneiss bedrock. The vegetation consists mainly of white birch/white spruce mixed forests, which occupy low-lying areas and cover up to 80% of the land area. The remaining habitats consist of shrubs and peat bog. Scrub birch, Serviceberry and Balsam Fir were once harvested in the boggy depressions of the island. There is a lighthouse and a lighthouse keeper’s residence and several other small buildings on the island.

Key biodiversity
An impressive number of colonial waterbirds use Île du Corossol in the breeding season. Three of these waterbirds, all larids, breed on the island in significant numbers. An average of 3,611 pairs of Herring Gull bred here between 1985 and 1998; the maximum colony size was 7,254 pairs in 1985. The average corresponds to about 3% of the North American Herring Gull population. About 1% of the North American population of Great Black-backed Gulls nests here. An average of 464 pairs nest here (1985-1998 average). The colony of Black-legged Kittiwakes is continentally significant. The three-survey average for this species is 2892 pairs - over 4,000 pairs were present in 1985 and 1988. The average represents about 1% of the Atlantic population.

The Double-crested Cormorant nests in close to continentally significant numbers, with just under 1% (or about 900 nests) of the Atlantic population nesting here.

Other breeding seabirds on Île du Corossol are: Black Guillemot (223 birds), Common Eider (581 pairs), Razorbill (815 birds), Common Murre (316 birds), and Leach’s Storm-Petrel (718 birds). Data is from the most recent survey in 1998. The Atlantic Puffin and Great Blue Heron appeared here recently, with puffins first noted during the 1996 surveys, and herons in 1998. The total number of all nesting seabirds was approximately 12,700 individuals in 1993, with a density of approximately 112 pairs per ha, and about 10,500 birds in 1998.

Recommended citation
BirdLife International (2023) Important Bird Areas factsheet: Corossol Island. Downloaded from on 01/04/2023.