Canvasback  (Aythya valisineria)

The canvasback is classified as Least Concern (LC) on the IUCN Red List (1).

Considered to be the ‘king’ or ‘aristocrat’ of North American ducks due to its distinctive profile, the canvasback (Aythya valisineria) is recognised by the long, stout neck and its thin, wedge-shaped head that slopes upwards from the top of the long bill to the back of the crown (3) (4).

The canvasback displays marked sexual dimorphism. The male has a chestnut-red head and neck, fading into blackish-brown on the face and crown. The breast is black, the back is greyish, and the flanks and belly are a contrasting white. The wing coverts are greyish, and the tail is blackish-brown. In contrast, the female canvasback has a light brown head and beak, with a slightly darker brown chest. The sides and back are greyish-brown. Both the male and female canvasback have a blackish bill and bluish-grey legs and feet (3) (5) (6) (7).

A migratory species, the canvasback breeds in prairie, parkland and sub-Arctic areas of the north-central U.S., western Canada and Alaska, and winters in coastal North America, as well as some inland sites in south-eastern U.S. and central Mexico (3) (5).

The canvasback mainly breeds in the aspen parklands of west-central Canada and the prairie-pothole regions of the United States, north to the subarctic boreal forests (3).

Outside of the breeding season, this species occupies a variety of costal marine and freshwater habitats, including estuaries, saltwater lagoons, brackish marshes, large, slow-moving rivers, lakes, open marshes, ponds, sewage lagoons, and occasionally flooded fields (3).

The canvasback feeds almost entirely by diving to consume the leaves, roots and seeds of aquatic plants. It usually dives to depths of around 2 metres when feeding, and remains submerged for 10 to 20 seconds, but will sometimes dive to depths of 9 metres (3). The canvasback will occasionally also feed at the water surface, either grabbing food items from the surface, or upending and submerging the head underwater. This species also eats a variety of insects, crustaceans and small fish (8).

Gregarious for most of the year, except when breeding, the canvasback is often seen foraging in large flocks. At migration stopover sites, extremely large flocks of over 1,000 individuals are often seen (3). Pair bonds are established during the spring northward migration, which commences in early February. Breeding birds arrive at the nesting grounds around early April, with the females often returning to the same site to breed each year (5) (9).

The female canvasback builds the nest, which is a bulky structure built on a mat of floating dead plants or suspended from emergent vegetation (3). Usually, 9 or 10 eggs are laid, and are incubated for around 24 days (2). The male canvasback usually abandons the female during incubation to gather with other males at moulting grounds and begin the southward migration (9).

The chicks, which have brownish upperparts and yellowish underparts, can fly at 63 to 77 days and reach sexual maturity at a year old (2). Most female and juvenile canvasbacks begin the southward migration in early September and arrive on the wintering grounds around late November (9).

The canvasback population has fluctuated greatly over the last century, partly as a result of it being a very popular game bird. During the early 1900s, the canvasback was hunted to near extinction, but closed shooting seasons along with improved nesting conditions allowed numbers to increase. However, in the 1930s, the population crashed once again, this time due to a series of droughts, which greatly reduced this species’ breeding success. Again the canvasback made a comeback, but in the 1960s and 1970s, the extensive drainage of prairie marshes resulted in a decline to around 500,000 individuals, a 50 percent reduction from numbers 20 years previously (6) (9) (10).

The canvasback population has since continued to fluctuate, partly due to changes in hunting regulations and moisture levels. Population highs generally correspond with periods of high water levels, which increases nesting habitat and reduces predation (3).

Today, the canvasback population appears to be in a slow decline (11), although it has recovered from historical crashes (3). Hunting is a less severe threat due to better management of harvests, but habitat loss is a continuing threat, while disturbance during breeding can cause nesting females to abandon the clutch. Oil spills and severe weather events, which can flood nests also threaten the canvasback, as does the ingestion of lead shot, pesticides and plastics (6) (9).

As a protected migratory game bird in Canada, the U.S., and Mexico, the canvasback has been the target of numerous management measures over the last three decades. These plans have employed different strategies to maintain population numbers, including changes in bag limits, the closure of certain areas to hunting and special canvasback hunting seasons (3).

In 1994, a canvasback harvest-management strategy was proposed by the Office of Migratory Bird Management, with one of its key objectives being maintaining a breeding canvasback population of at least 500,000. The canvasback has most likely also benefited from conservation actions implemented by the North American Waterfowl Management Plan, including the acquisition and restoration of land for the benefit of waterbirds (3).

Additional recommended conservation measures for the canvasback include public-awareness programmes at migratory stopover and nesting sites, to limit disturbance, as well as efforts to protect wintering sites with improved water quality. In addition, in the Canadian prairie-parklands, where agricultural expansion has significantly reduced habitat for breeding waterfowl, habitat restoration programs should focus on areas where the highest quality waterfowl habitat overlaps with the lowest quality agricultural lands. These areas offer greatest potential for affecting the recovery of breeding duck populations (3).

Find out more about the canvasback:

• Mowbray, T.B. (2002) Canvasback (Aythya valisineria). In: Poole, A. (Ed.) The Birds of North America Online. Cornell Lab of Ornithology, Ithaca.
  http://bna.birds.cornell.edu/bna/species/659
• BirdLife International - Canvasback:
  http://www.birdlife.org/datazone/speciesfactsheet.php?id=473