Like other birds, these large diving ducks exhibit seasonal and sexual dimorphism, meaning their feather color changes based on the season. Male canvasbacks have white bodies, black chests and tails, and a chestnut head during the breeding season. For the rest of the year, the males’ colors are more brown throughout. Females have pale, off-white bodies and gray-brown bodies and tails. 

Canvasbacks’ black bills seamlessly line up with their long, narrow and sloping heads.

Canvasbacks are the largest diving duck in North America. They are roughly 20 to 21 inches (50 to 53 centimeters) long and have a 31 to 35 inch (79 to 89 centimeter) wingspan. Both males and females on average weigh between 2.5 and 2.7 pounds (1.13 and 1.22 kilograms), with males being slightly larger.

During their spring and summer breeding season, canvasbacks are among many species of waterfowl that flock to North America’s flooded northern prairies, sometimes called the Prairie Pothole region. This region is part of the Great Plains and primarily focuses in the Upper Midwestern U.S. Here, these ducks live in temperate grasslands that are seasonally flooded with melted snow and spring rains, forming "potholes" of water that dot the landscape.

These ducks then fly south in the fall. They primarily winter on California or Texas coasts, or in northern to central Mexico. When selecting their wintering grounds, canvasbacks look for large bodies of water that contain large amounts of submerged aquatic vegetation. Historically, canvasbacks would also winter in the Chesapeake Bay. However, the continuing decrease of this favored food source has led to fewer ducks wintering there. 

Canvasbacks are not particularly loud ducks. Males will make a soft cooing vocalization to the females, who will answer with a soft “krrr krrr” sound.

Primarily diving for their food, canvasbacks mostly eat aquatic plants’ leaves, roots and seeds. Their preferred food is a plant called Valisineria americana, which is more commonly called celery root or wild celery. These diving ducks have also been known to eat mollusks, clams, insects and some small fish.

Canvasbacks are social birds when not breeding. They are often seen gathering in large flocks with other medium-to-large diving ducks like redheads and scaups during the winter.

Courtship and pair formation mostly occurs at stopover points throughout the canvasback’s spring migration. Canvasbacks are seasonally monogamous. After a female chooses her mate, they will stay together until the fall migration.

Canvasback nests are commonly found in marshes. The female canvasback will build the nest by herself with sturdy reeds and grasses. The bulky structure sits above water, on the stems of marsh plants.

Depending on the nesting site’s size and quality, canvasbacks will sometimes lay their eggs in another canvasback’s nest. Redhead ducks are known for laying their eggs in canvasback nests as well. These brood parasites are able to drop their eggs off because canvasbacks do not defend their nest site very well. If this does occur, the nest’s resident canvasback will lay less eggs.

On average, a female canvasback will lay between five to 12 eggs. Ducklings hatch after 23-29 days and are led into the water by the female within hours. Ducklings forage and feed themselves. Females stay with the ducklings for several weeks, but leave them before they fledge, which is around 60 to 70 days old.

In the 19th century, canvasbacks were heavily hunted for food. Hunters believe celery root, the canvasback’s favored food, made these ducks one of the most delicious game birds. Commercial market hunting almost drove canvasbacks to extinction. The Migratory Bird Treaty Act of 1918 was the first step toward saving this bird, as it outlawed market hunting.

Wetland habitat loss is another threat to canvasbacks and other diving ducks. Proceeds from the Duck Stamp, which must be purchased by every duck hunter in the United States, go toward conserving these wetland habitats.