In Pursuit of the Elusive “Bull Can”
The canvasback duck (Aythya valisineria) is a bold-looking and large member of the diving duck family. With its sloping forehead and large beak, it has a very distinct profile. And the drake’s starkly contrasting feathers and red eye help it stand out even more. Rarely venturing onto dry land, this diving duck lives most of its life on or in the water. A canvasback drake – commonly called a “bull can” or “king can” – deserves a spot on any waterfowl hunter’s list. If you haven’t had a chance to observe or hunt these amazing birds, here are some interesting details about them.
Description and Life History of the Canvasback
The canvasback is a large duck, measuring about 20 inches long and weighing 2 to 3 pounds on average (NatureServe 2020). Breeding drakes have chestnut/brown heads with bright red eyes and a black bill, black breasts and tails, and a bright white body and wings (All About Birds 2020). Females and non-breeding males (in eclipse plumage), on the other hand, have light brown heads, necks, breasts, and tails, and their body and wings are light gray/white (All About Birds 2020). Their legs are located far back on their body, which makes them awkward on land and forces them to take a swimming start before they can get airborne. But they are strong fliers, capable of reaching speeds of up to 56 miles per hour (All About Birds 2020). In flight, they can be readily identified by their bright white bodies, wings, and underwings, and dark heads and necks.
Canvasbacks start forming pairs during their spring migration back north. Drakes vie for female attention by putting on displays consisting of neck thrusts and clicking sounds. Hens construct and weave together floating nests of dead vegetation (e.g., grasses, reeds, rushes, sedges, cattails) in dense marshes, and line them with downy feathers (All About Birds 2020; National Audubon Society 2020). The hen usually lays 5 to 12 olive green eggs and incubates them alone for 23 to 29 days (All About Birds 2020; NatureServe 2020). Females may lay eggs in other duck’s nests, while redheads commonly do the same in canvasback nests (NatureServe 2020). Drakes leave the hens during incubation to molt in fresh or brackish wetlands before migration begins again in the fall, and they often live exclusively on the water at this time to avoid predators while they are flightless (All About Birds 2020). After hatching, the hen leads the ducklings to open water and stays with them for several weeks, although the ducklings can feed themselves.
Canvasbacks are diving ducks, which means they dive underwater to feed on vegetation and some insects or aquatic animals. They primarily feed on the leaves, roots/tubers, and seeds of wild celery, pondweeds, water lilies, wild rice, grasses, rushes, or sedges (National Audubon Society 2020; NatureServe 2020). In fact, the species name of the canvasback (valisineria) is similar to one of its preferred food sources, wild celery (Vallisneria americana). They also consume mollusks, aquatic insects, and small fish opportunistically, and hens and ducklings may focus more on these than plants (National Audubon Society 2020).
Since canvasbacks spend most of their lives on the water, most of their predators are also of the water. Typical predators of eggs, young, and adults include snapping turtles, pike, bald eagles, great black-backed gulls, black-crowned night herons, mink, and raccoons (BioKIDS 2020).
Range and Habitat of the Canvasback
Canvasbacks have a large annual range in North America. They are common breeders from Alaska and northern Canada down to the northwest half of the country and all through the prairie pothole region. In the spring and fall, they migrate across most of the rest of the United States. Finally, they spend their winters in California or along the Gulf Coast and up the Atlantic Coast to New England (National Audubon Society 2020).
As stated above, the canvasback is at home in the water. Therefore, its year-round habitats must include waterbodies of some sort. In summer, hens often nest and raise young in freshwater, shallow marshes. This may be in small marshes within the prairie pothole region or in large marshes further north and into the boreal forests of Canada (National Audubon Society 2020). Drakes use various marshes, lakes, bays, or ponds during the summer. During the winter, canvasbacks often form large rafts of thousands on deep interior lakes, rivers, lagoons, saltwater bays, and coastal estuaries (All About Birds 2020; NatureServe 2020).
Conservation Issues for the Canvasback
The canvasback is listed as globally secure and of Least Concern by the IUCN Red List (NatureServe 2020). The global breeding population is estimated to about 670,000 birds, and the North American Breeding Bird Survey suggests the population was relatively stable between 1966 and 2015 (All About Birds 2020). Despite that, loss of wetlands across the prairie pothole region has reduced breeding habitat, and fluctuations in water levels (due to droughts or alterations) can reduce nest sites in a given year, which may have an effect on the population numbers. Likewise, loss of one of their preferred food sources (wild celery) due to pollution or siltation has also affected migration routes and wintering area locations. Being a diving duck that feeds heavily on the bottoms of waterbodies, lead poisoning was a concern before the lead shot ban, but it has been reduced since then (NatureServe 2020). Hunters harvested about 114,495 canvasback ducks annually between 2012 and 2016, but that level is closely regulated to avoid over-harvest (All About Birds 2020).
Hunting Opportunities for the Canvasback
Unless you have access to many decoys and a good waterfowl boat/blind combination, it might be tough to break into hunting canvasbacks. But you can luck out occasionally if you’re diver duck hunting in the right flyway. California has the best opportunity for the Pacific flyway, while Texas and North Dakota are likely best for the Central flyway. In the Mississippi flyway, Minnesota, Wisconsin, Louisiana, and eastern Texas all usually have good harvest levels. Things are tough for those in the Atlantic flyway, but Maryland may still offer some shots.
Equipment and Bag Limits
Hunting canvasbacks requires most of the same duck hunting essentials as any species – a hunting license/federal duck stamp, a shotgun (12-gauge), non-toxic shotgun shells, camouflage clothing, a blind, and decoys. However, there is an issue of scale with canvasbacks. Since they commonly start forming huge rafts of ducks during migration, it can be tough to call a giant V-flock out of the sky with just a few dekes out. You may need dozens to get the right visual effect and entice a flock down. The current daily bag limit for canvasbacks is two birds.
Canvasback Hunting Techniques
If you really want to hit pay dirt your first time out, you might want to seek help from a knowledgeable friend or reputable guide. You should be able to find one somewhere along the Mississippi River, along the Gulf Coast, or in the plains states. Hunting big water with over a hundred decoys is rarely possible for a newbie waterfowl hunter. But a good waterfowl guide should be able to provide that. Likewise, hunting these powerful ducks on big water without a strong retrieving dog can reduce your chances due to crippled birds escaping.
If you’d like to try hunting canvasbacks on your own without the huge spread, there are a few pointers to consider. When you can only use a dozen decoys, focus most of them on drake canvasback decoys. The white drakes provide more of a visual cue for flocks flying over. Add some motion to the decoys to further enhance their realism. Also, feel free to mix in some puddle duck decoys, as you can usually find them mingling with mallards during migration. With any luck, you can add a large “bull can” to your species list too.
All About Birds. 2020. Canvasback. Accessed at: https://www.allaboutbirds.org/guide/Canvasback/id
BioKIDS. 2020. Canvasback. Accessed at: http://www.biokids.umich.edu/critters/Aythya_valisineria/
NatureServe. 2020. NatureServe Explorer: An online encyclopedia of life. Accessed at: http://explorer.natureserve.org
National Audubon Society. 2020. Guide to North American Birds. Accessed at: https://www.audubon.org/field-guide/bird/canvasback
Last modified: May 2, 2020