Mystery bird: canvasback, Aythya valisineria

Adult male canvasback, Aythya valisineria, sometimes known as the canvas-backed duck, photographed at Lake Merritt, Oakland, California, USA.

Image: Joseph Kennedy, 18 December 2010 [velociraptorize].
Nikon D200, Kowa 883 telescope with TSN-PZ camera eyepiece 1/160s f/8.0 at 1000.0mm iso400

Question: This remarkable North American mystery bird has been able to survive destruction of its feeding areas by radically changing its diet. Can you name the species and tell me what its favored diet was, and what it is now?

Response: This is an adult male canvasback, Aythya valisineria, in breeding plumage. This species is, to my eye, unmistakable in both silhouette and in colouring.

This bird's specific name, valisineria, is in honour of its favorite aquatic plant food; wild celery (eelgrass), Vallisneria americana. It uses its large bill to dig for roots and tubers of this and other aquatic plants in the muddy substrate of marshes and ponds. Originally, nearly all of the foods consumed by canvasback in the nonbreeding season were freshwater and estuarine plants, but now, these birds consume mainly Baltic clams, Macoma balthica, a small marine mollusk that is common in the Chesapeake Bay.

One of my favourite natural history books ever written is The Canvasback on a Prairie Marsh by H. Albert Hochbaum (ISBN 9780803272002; University of Nebraska Press, Lincoln, Nebraska; 1944). It's out of print now, but you can still find it if you search diligently for it online and in used book stores. This book is a stunning piece of scientific research and wildlife management, it is eminently readable and it includes many dozens of beautiful hand-drawn illustrations by the author.

You are invited to review all of the daily mystery birds by going to their dedicated graphic index page.

If you have bird images, video or mp3 files that you'd like to share with a large and (mostly) appreciative audience, feel free to email them to me for consideration.