Canvasback
The canvasback (Aythya valisineria) is a species of diving duck, the largest found in North America.
Taxonomy[edit]
Scottish-American naturalist Alexander Wilson described the canvasback in 1814. The genus name is derived from Greek aithuia, an unidentified seabird mentioned by authors, including Hesychius and Aristotle.[2]
The species name valisineria comes from the wild celery Vallisneria americana, whose winter buds and rhizomes are the canvasback's preferred food during the nonbreeding period.[3] The celery genus is itself named for seventeenth century Italian botanist Antonio Vallisneri.[2]
The duck's common name is based on early European inhabitants of North America's assertion that its back was a canvas-like color.[4] In other languages it is just a white-backed duck; for example in French, morillon à dos blanc, or Spanish, pato lomo blanco.[5] In Mexico it is called pato coacoxtle.[6]
Description[edit]
It ranges from 48–56 cm (19–22 in) in length and weighs 862–1,600 g (1.900–3.527 lb), with a wingspan of 79–89 cm (31–35 in). It is the largest species in the genus Aythya, being similar in size to a mallard but with a heavier and more compact build than it. 191 males wintering in western New York averaged 1,252 g (2.760 lb) and 54 females there averaged 1,154 g (2.544 lb).[7] The canvasback has a distinctive wedge-shaped head and long graceful neck. The adult male (drake) has a black bill, a chestnut red head and neck, a black breast, a grayish back, black rump, and a blackish brown tail. The drake's sides, back, and belly are white with fine vermiculation resembling the weave of a canvas, which gave rise to the bird's common name.[8] The bill is blackish and the legs and feet are bluish-gray. The iris is bright red in the spring, but duller in the winter. The adult female (hen) also has a black bill, a light brown head and neck, grading into a darker brown chest and foreback. The sides, flanks, and back are grayish brown. The bill is blackish and the legs and feet are bluish-gray. Its sloping profile distinguishes it from other ducks.[8]
Migration[edit]
The canvasback migrates through the Mississippi Flyway to wintering grounds in the mid-Atlantic United States and the Lower Mississippi Alluvial Valley (LMAV), or the Pacific Flyway to wintering grounds along the coast of California. Historically, the Chesapeake Bay wintered the majority of canvasbacks, but with the recent loss of submerged aquatic vegetation (SAV) in the bay, their range has shifted south towards the LMAV. Brackish estuarine bays and marshes with abundant submergent vegetation and invertebrates are ideal wintering habitat for canvasbacks.[8] A small number of birds are also known to have crossed the Atlantic, with several sightings being recorded in the United Kingdom. In December 1996, a canvasback was observed in a quarry in Kent, which was followed by an additional sighting in Norfolk in January 1997. At least five more sightings have since been confirmed in England.[9]
Cuisine[edit]
Canvasback ducks were a particularly prestigious game dish in mid-19th-century America. They were rarely found on everyday menus, and often featured at banquets. They were generally sourced from Maryland and Chesapeake Bay, and their flavor was attributed to their diet of wild celery. By the end of the century, though, they had become "scarce, expensive, or unobtainable".[12]
Edith Wharton refers to canvasback with blackcurrant sauce as an especially luxurious dinner served in New York City in the 1870s. Canvasback duck was a canonical element, along with Terrapin à la Maryland, of the elegant "Maryland Feast" menu, an "elite standard... that lasted for decades".[13]
Conservation[edit]
Populations have fluctuated widely. Low levels in the 1980s put the canvasback on lists of special concern, but numbers increased greatly in the 1990s.[14] The canvasback is particularly vulnerable to drought and wetland drainage on the prairies of North America.[8]
Many species of ducks, including the canvasback, are highly migratory, but are effectively conserved by protecting the places where they nest, even though they may be hunted away from their breeding grounds.[1] Protecting key feeding and breeding grounds is key for conserving many types of migratory birds.