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Severn River Coastline (ON135)


Severn River Coastline (ON135)

Moosonee, Ontario

Latitude 56.053°N
Longitude 87.638°W
Altitude 0 - 5m
Area 1,000.83km²

Site Description

The Severn River enters Hudson Bay about 200 km east of the Manitoba border. Fort Severn is located about 10 km upstream. The IBA includes the Severn River estuary; the coastline to the east for about 20 km to Beavertrap Creek; and the coastline to the west for about 25 km to Blackcurrent River. Supertidal marshes extend inland for 5 to 10 km, with some heath lichen tundra on low beach ridges. Partridge Island, a large marshy area, is located in the middle of the river mouth. Intertidal marshes, mudflats and submerged shoals extend offshore for at least a couple of kilometres. Numerous pools and ponds dot the supertidal marshes. This site lies within the tundra zone, and is in an area of permafrost with a mean daily temperature of - 5°C.


The coastline at the Severn River mouth has been long known as a significant staging area for large concentrations of waterfowl and other water birds. Although for the most part documentation of birds at this site is lacking, a few studies have suggested that this site is extremely important for geese, ducks and rails. Estimates of up to 40,000 Lesser Snow Geese, (greater than 1% of the estimated Hudson Bay population), have been suggested for this site. Specific counts include a one-day total of 10,000 Lesser Snow Geese during the fall of 1979, with only a small portion of the area being covered. Also in 1979, 4,000 Canada Geese (likely from the Mississippi Valley wintering population were recorded. In addition to staging geese, the site also appears to be significant for breeding and moulting ducks. However, very little quantitative information has been collected to document this usage. General descriptive comments include: high breeding densities, "highest in Ontario for Mallard"; and "would appear to rank in importance with major prairie moulting sites."

In 1940, over 100 Yellow Rails were heard from one spot in the marshes of this site. Although no recent counts have been completed, the birds are still known to occur at this site. Yellow Rails are now listed as Vulnerable in Canada by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).

Conservation Issues

Although hydroelectric developments on the Fawn / Severn River watercourses have been considered, there does not seem to be any interest in developing such a project at this time. Such a development could potentially affect the water levels considerably, resulting in the loss of marshes, mud and sand flats, as well as many other habitats.

IBA Criteria Habitats Land Uses Potential or Ongoing Threats Conservation Status
Yellow Rail
Number Year Season
Number Year Season