Bird of the Month: Canvasback
By Andy McCormick
Scientific Name: Aythya valisineria
Length 21 in
Wingspan 29 in
Weight: 2.7 lb
AOU Band code CANV
The Canvasback stands out from the crowd. Its stately presence separates it from other ducks. It has been called “the aristocrat of ducks” (Mobray), and “elegant” (Alderfer). Its large size, sloping forehead and characteristic “dark at both ends and white in the middle” appearance (Bell and Kennedy) make it easy to pick out of a group of other ducks. The male has a chestnut head and dark chest and tail. The head of the female is light brown. The flanks, back and inner wings are whiter in the male and grayer in the female. This feature gives the back the off-white color of undyed canvas which is the origin of its common name. Canvasbacks are generally silent.
It is the largest duck in its genus aythya ( a diving bird) which it shares in North America with Redhead, Common Pochard, Lesser and Greater Scaup, and Tufted Duck. Alexander Wilson through a misspelling, gave it the species name valisineria, because wild celery, Vallisneria americana, also called eel grass, is its favorite food (Holloway). It dives deeply to root out and eat the tubers of these and other aquatic plants. It is an omnivorous eater and will add snails, small clams and insect larvae to its diet especially during breeding season.
Canvasbacks breed in deep lowland ponds throughout northern North America including some in Eastern Washington such as the Pot Holes. The ducks form pairs during the spring migration and remain monogamous. The nest is constructed from the dead marsh vegetation in which it is sited, and a clutch of 7-12 eggs may be laid. The female incubates the eggs for 23-28 days and the young can fly after another 60 days.
There are a number of threats to Canvasback populations and the yearly fluctuation in their number is quite noticeable when they winter along the Washington coast. Their nests are often raided by Redheads who move out Canvasback eggs and deposit their own. This invasion has a reducing effect on the number of eggs laid by the Canvasback and leads them to abandon their nests. Canvasbacks are also popular birds for duck hunters. Management in years with low population has included bag limits, closure of some hunting areas, and a limit on Canvasback hunting days. In a related problem, these ducks forage in the sediment in waterways and the ingestion of lead shot is another concern for their health. In addition, wetland habitat degradation in wintering areas within the United States has been well documented for several decades. Despite these threats conservation and game management has had positive results and it is encouraging that Canvasback numbers have rebounded steadily since 1995 (Mobray).
These handsome ducks will begin arriving in Western Washington in mid-October and rafts of them can be seen on lakes, ponds and coastal estuaries throughout the winter. They are strong flyers and skilled divers giving them a special place in our ecology. Enjoy their visit to our coast.