"The Canvasback (Aythya valisineria), known in the United States as a "Sheldrake", is a large diving duck, up to 48-60 cm long and weighing 1270g.Their breeding habitat is North American prairie wetlands. The bulky nest is built from vegetation in a marsh and lined with down. Loss of nesting habitat has caused populations to decline. Canvasbacks usually take new mates each year, pairing in late winter.

Canvasbacks are strongly migratory and overwinter on the coasts of the United States, the Great Lakes and British Columbia in saltwater bays, estuaries or lakes. This species is also a very rare vagrant to western Europe.
Canvasbacks feed mainly by diving, sometimes dabbling, mostly eating aquatic plants with some molluscs, aquatic insects and small fish. Wild celery is a favourite food and is the origin of this bird's species name.
The canvasback sometimes lays eggs in other canvasback nests."