Monday, April 25, 2011

Canvasback

Canvasbacks, Aythya valisineria, are among our most uncommon ducks.  They are restricted to deep ponds, marshes and potholes.  During droughts, Canvasbacks often cease breeding.  Their numbers have also been adversely affected by drainage of prairie potholes and perhaps by over-hunting. 

Canvasbacks are expert divers.  They often feed in shallow water, but can submerge to over 30 feet.  They consume aquatic plants and a variety of invertebrates.  In the winter they specialize on Wild Celery, Vallisneria americana, which accounts for their scientific name (Mowbray 2002).

The Canvasbacks in this post are a female (first photo) from St Marks National Wildlife Refuge on the Florida panhandle during our February jaunt, and (below) two males from Sand Lake National Wildlife Refuge in northeastern South Dakota taken several years ago.  Redheads and Canvasbacks look somewhat similar but are easy to identify.  Canvasbacks have "ski-slope" foreheads and bills.  Redheads have a much more typical duck profile.  The white backs of male Canvasbacks are visible from considerable distances.

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