Bird of the Month November 2020

Canvasback  

Aythya valisineria

BASIC DESCRIPTION

Canvasback ducks are large diving ducks. Both males and females have stout necks and a chest darker than the body. Instead of a distinct brow, the forehead slopes generally in line with the bill. The male Canvasback is particularly handsome in breeding season. He sports a red eye, red-brown head and neck (the head is almost black on top), black chest and tail and a silvery white body. Females are similar but less flamboyant and have a dark eye.

Behavior and Habitat

Like all diving ducks, Canvasbacks need a “runway” for take-off. They do not spring out of the water like a Mallard might.

Many ducks utilize grainfields and other terrestrial habitats at different times. That is much less true for the Canvasback. This duck spends most of its time on the water, sleeping with head tucked under wing and even building its nest over water.

Canvasbacks eat mostly plant rhizomes and tubers, snatching them from up to seven feet deep in marshes and ponds. During breeding season they are much more omnivorous eating a mix of plant and animal matter.

Hens construct the nest and lay as many as 11 eggs. Males leave about halfway through incubation and head to molting grounds where they will be flightless for a period of time. Hens raise the brood alone.

Other than during breeding or when resources are scarce, Canvasbacks are social birds, often forming rafts of hundreds or even thousands of birds.

Cool Facts from All About Birds website

  • The species name of the Canvasback, valisineria, comes from Vallisneria americana, or wild celery, whose winter buds and stems are the duck’s preferred food during the nonbreeding period.
  • In the world of ducks, females abide by the saying, “don't put all your eggs in one basket.” Female Canvasbacks sometimes lay eggs in another Canvasback's nest; and Redheads and Ruddy Ducks sometimes lay their eggs in a Canvasback's nest.
  • The oldest recorded Canvasback was a male, and at least 22 years, 7 months old when he was shot in California in 1991. He had been banded in the same state in 1969.

Similar Species

The Canvasback is most likely to be confused with the Redhead Duck. There are four distinctions though that make the males easy to differentiate. First, look for the sloping forehead on the Canvasback. The Redhead will have a distinct brow and forehead. Second, the head and neck of the Redhead is truly red and evenly colored while that of the Canvasback is more red-brown and darker on top. Third, the body of the Canvasback is white while that of the Redhead is more gray. Fourth, the Redhead has a yellow and not a red eye.

When and where found at Camas NWR

Canvasbacks are common visitors to the Refuge during the fall according to the Refuge bird list. Look for them in the more open and deeper waters of the wetlands.

Conservation

“Canvasback populations have fluctuated widely since the 1950s. Low numbers in the 1980s put the Canvasback on species of special concern lists, but numbers increased greatly in the 1990s. The North American Breeding Bird Survey suggests that the population has been stable from 1966 through 2015. In 2017, the U.S. Fish and Wildlife Service estimated the U.S. population at around 700,000 individuals. Partners in Flight estimated the global breeding population at 670,000. The species rates a 10 out of 20 on the Continental Concern Score, which means it is not on the Partners in Flight Watch List and is a species of low conservation concern. Fluctuations in numbers are likely due to wetland loss and to changes in water levels that reduce the number of available nest sites. The suggestion is that Canvasbacks did well in wet years and poorly in dry years. In the Prairie Provinces in Canada around 40% of original wetlands were lost between 1951 and 1981. In North and South Dakota 3.6 million acres of wetlands have been lost and another 3.6 million were lost in Minnesota. Loss of wild celery, a primary food source, due to pollution, siltation, and eutrophication also made some areas useless for Canvasbacks; their migration routes and wintering sites changed during the last 40 years as a result. Hunting may also contribute to fluctuations as harvest limits have changed over the last 3 decades. The U.S. Fish and Wildlife Service manages duck hunting and limits the number of individuals hunters can take every year based on population size. From 2012–2106, hunters took on average 114,495 Canvasback annually.” www.allaboutbirds.org/guide/canvasback/lifehistory

Text by Terry Thomas. Source: https://www.allaboutbirds.org

Photo by Terry Thomas.