Least Bittern in Carden

Ron Pittaway

First published in Toronto Ornithological Club Newsletter, November 2018, No 281.

Photo by Jean Iron


The secretive Least Bittern is near the northern edge of its breeding range on the Carden Alvar. It is listed as Threatened in Canada by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). The greatest threat to this species is the loss of marshes.

IDENTIFICATION: The Least Bittern is tiny, barely larger than a meadowlark, but with a longer neck and longer legs. It is most often seen when it flushes with dangling legs and flies low for a short distance before dropping back into cover. On flying and perched birds, note the buffy inner wing patches as shown in the photo.

SONG and CALL: Peak activity periods are dawn and dusk. The male's song (also heard at night) is a series of five or six low cuckoo-like notes coo-coo-coo-coo-coo repeated at regular intervals. Its cackling kek-kek-kek-kek call could be mistaken for a railís call.

WHEN: The best time to see a Least Bittern is after the eggs have hatched starting about mid-June. The adults become more visible when bringing food to their young, often flying in broad daylight. The parents feed young for up to 30 days.

WHERE: Watch and listen for Least Bitterns by the channel at the Prospect Road Marsh and in cattails along Centennial Park Road 33. In the 1990s, Brian Henshaw and I canoed Cranberry Lake where we saw Least Bitterns in ideal habitat. The Sedge Wren Marsh is unsuitable habitat for Least Bitterns because it is a shallow water marsh dominated by sedges and grasses.

HABITAT: Least Bitterns prefer large deep cattail marshes with scattered areas of open water. They are most numerous in young marshes known as the hemi-marsh stage, which have an interspersion of 50% emergent vegetation and 50% open water. Productive marshes begin to stagnate in about 10 years.

MARSH MANAGEMENT: Many marshes, including the Prospect Road Marsh, are filling in with dense vegetation. They are in an old or lockup stage with most of their nutrients stored in organic plant matter, and they have a low biodiversity and fewer marsh birds. Unproductive marshes need rejuvenation to restore hemi-marsh conditions for Least Bitterns, Pied-billed Grebes, Common Gallinules and other marsh birds. Hillman Marsh Conservation Area and Tiny Marsh Provincial Wildlife Area are examples of managed wetlands.

ACKNOWLEDGMENTS: I thank Michel Gosselin for proofing and Jean Iron for the photo.