email a friend
printable version
Location Canada, Ontario
Central coordinates 87o 36.61' West  56o 5.97' North
IBA criteria A4iii
Area 62,500 ha
Altitude 0 - 5m
Year of IBA assessment 2008

Bird Studies Canada/Nature Canada

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.

Key Biodiversity 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).

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
A4iii Species group - waterbirds passage  1995  20,000-49,999 individuals  unknown  A4iii   


IUCN habitat Habitat detail Extent (% of site)
Shrubland Scrub  -
Grassland Tundra  -
Wetlands (inland) Bogs; Estuarine waters; Fens transition mires & springs; Freshwater marshes/swamps; Intertidal mud, sand or salt flats; Salt/brackish marshes  -
Sea Open sea  -

Land use

Land-use Extent (% of site)
hunting major

Contribute  Please click here to help BirdLife conserve the world's birds - your data for this IBA and others are vital for helping protect the environment.

Recommended citation  BirdLife International (2016) Important Bird and Biodiversity Area factsheet: Severn River Coastline. Downloaded from on 24/10/2016

To provide new information to update this factsheet or to correct any errors, please email BirdLife