The Spruce Island Reefs are located in the northern part of Lake Winnipegosis in Manitoba. Lake Winnipegosis is a large (5,403 km2), shallow (maximum depth ~55 m), freshwater lake with many small islands. Deciduous and coniferous forests border Lake Winnipegosis, with large expanses of freshwater marsh occurring along the lake. The habitats of these islands are unrecorded, but are assumed to be as noted here.
The Spruce Island Reefs support globally significant numbers of Caspian Terns, and a large mixed colonial waterbird colony. Approximately 3,000 Caspian Terns nested on the Spruce Island Reefs in 1999. This represents over 9% of this species North American population, and may be the largest Caspian Tern colony in Canada. Also, over 1% of the estimated Canadian population of American White Pelican also nest on these islands - in 1999, 760 nests were found.
Common Tern, Double-crested Cormorant, Ring-billed Gull, and Herring Gull also breed on the reefs. A 1999 survey found 200 Common Tern nests, 1,351 Double-crested Cormorant nests, 3,498 Ring-billed Gull nests, and 43 Herring Gull nests. Thus, in total 8,852 nests of colonial waterbirds, or about 17,700 birds, breed here.
BirdLife International (2021) Important Bird Areas factsheet: Spruce Island Reef. Downloaded from http://www.birdlife.org on 29/11/2021.