The Shagamu River enters Hudson Bay about half way between the Severn River to the west and the Winisk River to the east. The site encompasses both sides of the mouth of the Shagamu River for about 40 km east to Ministick Creek and 30 km west to Beavertrap Creek. Numerous beach ridges are located parallel to the coast, with hollows containing thousands of small ponds and lakes. Near the coast, supertidal marshes occur inland, with extensive intertidal marshes and submerged shoals extending well offshore. The raised beach ridges are vegetated with scattered graminoids, and these ridges becoming covered with heath tundra and scattered spruces as one progresses inland. These coastal beach ridges are an important calving area for Woodland Caribou (designated as nationally vulnerable).
Shorebirds and waterfowl occur at this site in large numbers during both the spring and fall migration. During a 1993 study, significant one-day counts were recorded for two shorebird species: Hudsonian Godwit (920 over 1% of the worlds estimated population) and Pectoral Sandpiper (900 over 2% of the worlds estimated population). Up to 600 American Golden-Plovers have also been recorded during one-day counts. Large numbers of Lesser Snow Geese and Canada Geese have also been recorded at this site during both the spring and fall migrations. Notable numbers include one-day counts of over 20,000 Lesser Snow Geese in both the spring and fall and almost 10,000 Canada Geese in the fall. (The Canada Geese were likely from either the Tall Grass Prairie or the Mississippi Valley populations.)
In addition to staging geese and shorebirds, significant numbers of Black Scoters gather in moulting flocks of the coastline. Aerial surveys during the late summer of 1994 resulted in an estimate of 43,700 birds (as much as 21.8% of the estimated eastern North American population).
Conservation responses/actions for key biodiversity
The eastern half of this site is located within Polar Bear Provincial Park. No major conservation issues or threats are known.