The canvasback (Aythya valisineria) is a species of diving duck found in North America. The males (drakes) and females (hens) have distinct plumage differences that can be used to tell them apart. Canvasbacks are large diving ducks with long, sloping bills and elongated necks and bodies. They are found primarily in the Prairie Pothole region of North America. Canvasbacks feed by diving and consume aquatic vegetation, seeds, mollusks, and crustaceans. They nest in emergent aquatic vegetation.
Identification
There are several key differences between drake and hen canvasbacks:
Plumage
- Drake canvasbacks have a distinctive brownish-red head and neck. Their back is black grading into pale gray on the rump and uppertail coverts. Their chest is white.
- Hen canvasbacks have a light brown head and neck. Their back is brownish-gray and their chest is grayish-brown.
Bill Color
- Drake canvasbacks have a blackish bill.
- Hen canvasbacks have a dull grayish bill.
Eye Color
- Drake canvasbacks have a bright red eye.
- Hen canvasbacks have a brown eye.
The differences in head color and bill color are the most obvious identifiers between drake and hen canvasbacks when observed in the field. The drake’s red head is unmistakable.
Size
Both drake and hen canvasbacks are large diving ducks, but there are some subtle size differences:
- Drakes tend to be slightly larger, with an average length of 20-22 inches and wingspan of 32-36 inches.
- Hens are smaller, with an average length of 17-19 inches and wingspan of 29-31 inches.
There is considerable overlap in size and it may be difficult to distinguish a large hen from a small drake based on size alone. Weight is similar, with drakes averaging 2-2.5 pounds and hens averaging 1.5-2.1 pounds.
Behavior
Drake and hen canvasbacks exhibit some slightly different behaviors, especially during breeding season:
Aggression
- Drakes are more aggressive than hens and defend breeding territories from other drakes.
- Hens are not territorial.
Courting Displays
- Drakes perform elaborate courtship displays to attract hens, including neck stretching, head throws, and swimming circles around hens while cooing.
- Hens may incite displays from drakes but do not perform ritualized displays.
Parental Care
- Only the hen incubates the eggs and cares for the ducklings.
- Drakes leave shortly after mating and do not participate in parental care.
Breeding And Nesting
There are some key differences in breeding ecology between drakes and hens:
Breeding Season
- Canvasbacks breed May through July across the Prairie Pothole region.
- Drakes arrive at the breeding grounds before hens to establish territories.
Mating System
- Canvasbacks exhibit a polygynous mating system where male drakes may mate with multiple females.
- Pairs form each breeding season rather than mate for life.
Nest Sites
- Hens build nests concealed in emergent vegetation near open water.
- Preferred nesting habitat includes bulrush, cattails, and reeds.
Clutch Size
- Hens lay an average of 8-10 eggs.
- Only the hen incubates the eggs for 24-25 days.
There are no paternal responsibilities for drakes in terms of nest-building, incubating, or rearing young. Their key role is mating with hens.
Dietary Differences
Both canvasback drakes and hens are omnivorous dabbling and diving ducks, feeding on:
- Aquatic plants (especially wild celery, pondweeds, widgeongrass)
- Insects
- Mollusks
- Crustaceans
- Fish eggs
- Seeds and tubers
There are no major dietary differences between the sexes. However, hens may consume more protein-rich foods like aquatic invertebrates during egg production.
Population Status
- The canvasback population declined in the early 20th century due to hunting pressure and habitat loss.
- Conservation measures were implemented in the 1930s and populations rebounded to around 700,000 birds.
- Canvasback numbers remain healthy with an estimated population of 625,000.
- They are not considered threatened or endangered.
Population trends do not differ between male and female canvasbacks. Both sexes experienced concurrent declines and recovery over the past century.
Conclusion
In summary, drake and hen canvasbacks can be distinguished by differences in plumage coloration, bill and eye color, and size. Behaviorally, drakes are more aggressive and perform elaborate courtship displays while hens solely incubate eggs and care for ducklings. Both sexes utilize similar habitats and consume the same foods, although hens may eat more protein-rich items when forming eggs. Plumage differences remain the most reliable way to differentiate drakes from hens in the field. Understanding these differences allows for proper identification and appreciation of canvasback natural history.