Lake St. Martin is located between Lake Manitoba and Lake Winnipeg. Water from Lake Manitoba flows to Lake St. Martin via the Fairford River, and Lake St. Martin flows into Lake Winnipeg through the Dauphin River. Not much is known about the vegetation on the islands within the lake, but they are low-lying and likely far enough offshore to provide protection from predators. The surrounding shoreline of Lake St. Martin is generally flat and often marshy.
The islands of Lake St. Martin support significant numbers of several colonial waterbird species: terns, cormorants, and pelicans. A total of 3,400 Common Tern nests were recorded at this site, representing about 3% of the estimated North American population of this species. And in 1986, 1,500 Caspian Tern nests were recorded on a reef in Lake St. Martin. This number of nests is roughly equivalent to 4.5% of the North American Caspian Tern population.
Double-crested Cormorants also occur in large numbers at this site. In 1991, 2,414 cormorant nests, or about 1.6% of the Interior cormorant population, were observed at this site. Hundreds of American White Pelicans nest here too, although a recent estimate is not available. In 1969, 670 nests were counted and if increases in the overall population of pelicans also occurred here, then the population on these islands may equal about 1% of the Canadian population of the species.
Small numbers of Great Blue Herons and Black- crowned Night-Herons breed on islands within the lake. Twenty Great Blue Heron nests were recorded on an unnamed island in 1979, and another 20 nests were recorded on Big Fisher Island in 1991. Moderate numbers of ducks and geese breed and migrate amongst the Lake St. Martin Islands, and small numbers of Forsters Terns have nested in the past in the marshes bordering Lake St. Martin. Bald Eagles have been recorded as both a breeding and a staging species - it is thought that they are attracted to the fish that spawn at the mouth of the Dauphin River.
BirdLife International (2021) Important Bird Areas factsheet: Lake St. Martin Islands. Downloaded from http://www.birdlife.org on 19/10/2021.