The canvasback feeds mainly by diving, sometimes dabbling, mostly eating seeds, buds, leaves, tubers, roots, snails, and insect larvae.
Besides its namesake, wild celery, the canvasback shows a preference for the tubers of sago pondweed, which can make up 100% of its diet at times.
The canvasback has large webbed feet adapted for diving and its bill helps it dig tubers from the substrate.
In the late 1930s, studies showed that four-fifths of the food eaten by canvasbacks was plant material.

In the early 1950s it was estimated that there were 225,000 canvasbacks wintering in the Chesapeake Bay; this represented one-half of the entire North American population.
By 1985, there were only 50,000 ducks wintering there, or one-tenth of the population.
Canvasbacks were extensively hunted around the start of the 20th century, but federal hunting regulations now restrict their harvest, so hunting is ruled out as a cause for the decline.
Scientists have now concluded that the decline in duck populations was due to the decline in SAV acreage.
Today the population has stabilized and is even increasing slightly, although it is nowhere near previous levels.
Studies have now shown that by the 1970s four-fifths of the ducks' diet was made up of Baltic Clams, which are very common in the Chesapeake Bay: the ducks have been able to adapt to the decline in SAV by changing their diet.
Redheads, which also feed on SAV tubers, have not been able to adapt, and their population remains low.
Canvasbacks are omnivores, eating everything from seeds to plant tubers and from mussels to insects.
During the breeding season they eat both plant and animal foods, but during migration and winter they primarily eat rhizomes and tubers from aquatic plants.
Canvasbacks dive straight down to depths of around 7 feet to extract pieces of aquatic plants with their bill.
Other food is taken from or just below the surface of the water.
The canvasback feeds mainly by diving, sometimes dabbling, mostly eating seeds, buds, leaves, tubers, roots, snails, and insect larvae. Besides its namesake, wild celery, the canvasback shows a preference for the tubers of sago pondweed, which can make up 100% of its diet at times. The canvasback has large webbed feet adapted for diving and its bill helps it dig tubers from the substrate. In the late 1930s, studies showed that four-fifths of the food eaten by canvasbacks was plant material. 
In the early 1950s it was estimated that there were 225,000 canvasbacks wintering in the Chesapeake Bay; this represented one-half of the entire North American population. By 1985, there were only 50,000 ducks wintering there, or one-tenth of the population. Canvasbacks were extensively hunted around the start of the 20th century, but federal hunting regulations now restrict their harvest, so hunting is ruled out as a cause for the decline. Scientists have now concluded that the decline in duck populations was due to the decline in SAV acreage. Today the population has stabilized and is even increasing slightly, although it is nowhere near previous levels. Studies have now shown that by the 1970s four-fifths of the ducks' diet was made up of Baltic Clams, which are very common in the Chesapeake Bay: the ducks have been able to adapt to the decline in SAV by changing their diet. Redheads, which also feed on SAV tubers, have not been able to adapt, and their population remains low. Canvasbacks are omnivores, eating everything from seeds to plant tubers and from mussels to insects. During the breeding season they eat both plant and animal foods, but during migration and winter they primarily eat rhizomes and tubers from aquatic plants. Canvasbacks dive straight down to depths of around 7 feet to extract pieces of aquatic plants with their bill. Other food is taken from or just below the surface of the water.
Canvasback