Manitoba Bird Bird Atlas: Species At Risk

Least Bittern

Early Breeding and Last Migration Dates

South: Regions 1 to 8 Central: Regions 9 to 12 North: Regions 13 and 14
Early Breeding Last Migration Late Breeding Early Breeding Last Migration Late Breeding Early Breeding Last Migration Late Breeding
May-01 Jun-01 Aug-16

Breeding Evidence

Least Bitterns breed strictly in marshes dominated by emergent vegetation surrounded by areas of open water, most often in marshes dominated by cattails. However, breeding also occurs in areas with other robust emergent plants and in shrubby swamps. The presence of stands of dense vegetation is essential for nesting because the nests of Least Bitterns sit on platforms of stiff stems (image to the left). The nests are almost always within 10 meters of open water. Open water is also needed for foraging, because Least Bitterns forage by ambushing their prey in shallow water near marsh edges, often from platforms that they construct out of bent vegetation. Access to clear water is essential for the birds to see their prey.


Breeding Evidence Map

Least Bitterns are small herons; they prefer large marshes that have relatively stable water levels throughout the nesting period.

They are found in south-central Manitoba in a triangluar-shaped area with its base on the border and its apex in the Interlake. They are found in wetlands near Whitemouth, Spruce Siding, and Oak Hammock Marsh. However, they have also been observed near Churchill, Glenboro, Gypsumville, Oak Lake, The Pas, and York Factory. They may be expanding their range westward as the number of sightings in western Manitoba around Whitewater Lake and Carberry is increasing in recent years.

-from COSEWIC and The Birds of Manitoba (p. 85)