CANVASBACK. An American fresh-water duck (Aythya rallisneria), regarded as superior to all others for food. It breeds from Dakota northward, but most numerously in the far north, making its nest on the ground. in a marsh, and laying six to ten greenish-buff eggs. (For illustration, see Plate of DUCKS, WILD.) The eanynsbneks begin to come southward along in land waterways in November, and spread over all the Middle and Southern United States. They are attracted in greatest numbers to the extensive marshes and river fiats about Lakes lluron and Erie and around Chesapeake Bay. but are also irregularly numerous wherever their favorite food grows in the Mississippi Valley and on the ‘slews' of the plains. This food is the wild celery (Zostera rollisneria), which grow: densely on fresh-water shoals in from 7 to 9 feet of water, like a tall grass, the root of which is white and has some resemblance to small celery. "Wherever this plant grows in abundance, the canvasbacks may be expected," says Wilson: "while in waters unproyided with this nutritious plant they arc altogether un known. . . . They float about these shoals, diving and tearing up the grass by the roots, which is the only part they eat." lt is not quite
true to say that they will eat nothing else, for celery is not always available. They are ex tremely shy, quick and strong in flight, and re markably expert in diving, so that all the skill and strategy at the disposal of the gunner is necessary to success in shooting them. They are so relentlessly pursued, however, that their numbers are far less in all their haunts than formerly; and very many of the alleged can vasbacks sent to market are really redheads (q.v.), a closely related and nearly as good duck, of similar habits, but less strongly addict ed to the celery diet. The male canvasback has a bead reddish, but much obscured with dusky tints, while that of the redheaa is clear, bright chestnut, and the hill is blackish (not blue). The back and sides are whitish (less dark than that of the redhead), marked with sparse, wavy lines and dots, suggesting the surface of coarse canvas. The fore part of the body, rump, and tail-coverts are black; speculum, bluish-gray; length, about 20 inches. Consult Elliott, Wild Fowl of North America (New York, I808).