Canvasback: The Largest Diving Duck in North America
The canvasback (Aythya valisineria) is a species of diving duck that is native to North America. It is the largest member of its genus, with a distinctive wedge-shaped head and a long graceful neck. The canvasback is named for its white back, which resembles the weave of a canvas. The canvasback feeds mainly on aquatic plants, especially wild celery, which gives its scientific name.
In this article, we will explore the biology, behavior, and conservation status of the canvasback, as well as some interesting facts about this remarkable bird.
Biology of the Canvasback
The canvasback ranges from 48â56 cm (19â22 in) in length and weighs 862â1,600 g (1.900â3.527 lb), with a wingspan of 79â89 cm (31â35 in). The male (drake) has a chestnut red head and neck, a black bill, breast, rump, and tail, and a white body with fine vermiculation. The female (hen) has a light brown head and neck, a black bill, and a grayish brown body. Both sexes have bluish-gray legs and feet and bright red eyes in the spring.
The canvasback is adapted for diving and foraging underwater. It has a large and powerful bill that can dig up the roots and rhizomes of aquatic plants. It also has large webbed feet that propel it through the water. The canvasback can dive up to 6 m (20 ft) deep and stay submerged for up to 15 seconds.
Behavior of the Canvasback
The canvasback breeds in prairie potholes and subarctic river deltas in North America. It prefers to nest over water on permanent marshes surrounded by emergent vegetation, such as cattails and bulrushes, which provide protective cover. The female builds a bulky nest from vegetation and lines it with down. She lays 7-12 olive-gray eggs and incubates them for 23-28 days. The male usually leaves before the eggs hatch and joins other males in molting flocks.
The young are precocial and leave the nest within hours of hatching. They are led by the female to open water where they feed themselves on aquatic insects and plants. The female stays with them for several weeks but departs before they fledge. The young are capable of flight at about 60-70 days of age.
The canvasback migrates in large flocks, often in V-formation, to coastal bays and estuaries in winter. It also winters on some inland lakes where open water is available. The canvasback is highly social and forms mixed flocks with other diving ducks, such as redheads, scaups, and ring-necked ducks. The canvasback is mostly silent but may utter some low grunts or whistles during courtship or when alarmed.
Conservation Status of the Canvasback
The canvasback is classified as Least Concern by the IUCN Red List of Threatened Species. However, its population has been declining for some time due to habitat loss, overharvesting, pollution, and competition from invasive species. The main threat to the canvasback is the loss of nesting habitat in prairie wetlands, which have been drained or converted to agriculture. The canvasback also faces reduced food availability in wintering areas due to eutrophication, sedimentation, and herbicide use that affect aquatic vegetation growth.
The canvasback is protected by the Migratory Bird Treaty Act in the United States and Canada, and by similar laws in Mexico. It is also monitored by various surveys and banding programs that track its population trends and movements. Some conservation measures that have been implemented or proposed for the canvasback include restoring and protecting wetland habitats, regulating hunting seasons and bag limits, reducing contaminants in waterways, and managing invasive species such as carp and zebra mussels that compete with or prey on aquatic plants.