Lake St. Martin Islands

Year of compilation: 2001

Site description
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.

Key biodiversity
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.

Conservation responses/actions for key biodiversity
Given that the numerous waterbirds that breed here consume fish as a large part of their diets, it is possible that local fishermen may not support the conservation of these birds. Although these bird species are known to largely eat non-game species, in some locations fisherman perceive these birds as threats to local fish stocks and occasionally illegally kill many cormorants, and in some cases herons and possibly terns.

Nearby aboriginal communities use the area for hunting, fishing, and trapping, but this site is not well known by ornithologists and more bird surveys are needed.

Recommended citation
BirdLife International (2022) Important Bird Areas factsheet: Lake St. Martin Islands. Downloaded from on 01/10/2022.