Aythya is a genus of diving ducks. It has twelve described species. Aythya shihuibas was described from the Late Miocene of China. An undescribed prehistoric species is known only from Early Pleistocene fossil remains found at Dursunlu, Turkey; it might however be referrable to a paleosubspecies of an extant species considering its age. The Miocene “Aythya” arvernensis is now placed in Mionetta, while “Aythya” chauvirae seems to contain the remains of 2 species, at least one of which does not seem to be a diving duck.
In early autumn, the young of both sexes resemble adult females, although their breast plumage is more mottled and their back plumage is darker. During November, the young males begin to resemble the adult males, and by February the adult plumage of both sexes has almost completely grown in.
The genus Aythya to which the Canvasback belongs includes 12 species, five of which occur in North America. These are the Canvasback, Redhead, Greater Scaup, Lesser Scaup, and Ring-necked Duck. Generally, all Aythya species have rounded bodies with large feet, legs set back on the body, and a broad bill. They are all diving ducks.
Listen to the sound of Canvasback
Copyright remark: Most sounds derived from xeno-canto
|wingspan min.:||79||cm||wingspan max.:||89||cm|
|size min.:||48||cm||size max.:||56||cm|
|incubation min.:||24||days||incubation max.:||29||days|
|fledging min.:||56||days||fledging max.:||29||days|
On their winter feeding grounds, they often form small compact flocks and fly about for pleasure, especially in the early morning and the late afternoon. Their wings create a loud whirring noise.
Wild ducks feed either by dabbling on the surface of the water, or by diving below the surface. Although Canvasbacks dabble at times, they are diving ducks because they usually dive for their food and because, like other divers, they have a special lobe on their hind toe that they use like a paddle in the water.
Canvasbacks do not mate for life. Pairs form in late winter or during migration in early spring, and the female leads her mate to a nest site, usually near where she was reared. This species nests late, usually about the end of May.
Canvasbacks commonly build their nests near open water in the shallows of large sloughs, or marshy areas, among cattails, bulrushes, and reeds. The nest is a large, bulky structure made of reeds and sedges and lined with drab brown down plucked from the female’s body. As incubation, or warming of the eggs until they hatch, proceeds, the layer of down thickens into an insulating blanket. The female uses this to cover the eggs when she leaves the nest.
As soon as the females have laid their seven to nine eggs, the males desert their mates and gather in large flocks on lakes and larger sloughs to moult, or shed old feathers. For two weeks, the males are unable to fly to escape predators due to loss of their flight feathers. Their plumage changes colour to look like that of the females, which is more effective camouflage, while they wait for new flight feathers to grow in.
The burden of incubating the eggs and rearing the brood falls on the females alone, and hens younger than five years old are frequently unsuccessful. The drab green or grayish olive eggs must be incubated for 24 to 28 days. A day or two after the eggs have hatched, the ducklings must be led safely to open water to find their own food, usually drifting plant material. The young do not develop feathers until about the fifth week, and are unable to fly until about 11 weeks.
In late summer, the females and young join the males. Family units split up during the early fall, and the young may or may not migrate with their parents.
In Nederland zeldzame dwaalgast met twee bevestigde waarnemingen.
In the last 40 years, Canvasback populations have fluctuated from about 500 000 in the mid-1950s to about 200 000 in the early 1990s. In an attempt to ensure that populations remain healthy, the Canadian and American governments regulate hunting carefully. The Canadian Wildlife Service and the United States Fish and Wildlife Service, in conjunction with provincial and state wildlife agencies, conduct surveys to determine total numbers of ducks and the annual hunting kill.
Restrictive hunting regulations are not enough to ensure healthy populations. Loss of habitat and periodic droughts on the breeding grounds cause declines in populations of this and other species. Loss of habitat results from farmers and developers draining wetlands and the use of vast expanses of former breeding range to grow crops. In addition, wintering range has been reduced in quality. For example, Chesapeake Bay, Maryland, no longer supports the wide range of plants that wintering Canvasbacks once fed upon.
Concern for the Canvasback and other wild ducks and geese that nest in prairie wetlands has prompted the various federal, provincial, and state wildlife agencies to cooperate in programs called “habitat joint ventures” under the North American Waterfowl Management Plan, or NAWMP. Programs to enhance wetlands used by ducks and geese have been initiated in Canada, the United States, and Mexico.