Adult Male
Summer Plumage:
The head and the anterior upper neck are dark brownish-black. The nape is a muted black, gradually transitioning to brown towards the head and becoming grey towards the posterior neck. A white band originates on both sides of the nape, extends laterally, and joins at the front of the neck and chest. In some individuals, this white area may be speckled with faint black or greyish-brown, especially on the front of the neck, and tinged with reddish-brown on the chest. The posterior neck, sides of the chest, shoulders, back, flanks, and abdomen have narrow grey and brown streaks. These streaks are darker on the back and sides of the chest than on the abdomen. The back and undertail coverts are brown with indistinct grey streaks. The upper tail feathers are black with grey edges.
The longest shoulder feathers are black with grey edges and brown streaks; the shorter shoulder feathers resemble the back, but have dark streaks down the center. The wing coverts are pale grey-brown. The largest wing coverts have reddish-brown tips, forming a band in front of the speculum. The speculum is iridescent copper-green, bordered by black and white. The flight feathers are grey and pale black.
The central tail feathers are long and pointed, black in color, while the other feathers are grey-brown. The undertail is black, except for the white feathers on the sides. The area near the tail on the posterior flanks is white, with a slight yellowish-brown hue.
Winter Plumage:
Resembles the female’s plumage; except the wings remain unchanged from the summer plumage.
Female
The dorsal surface is brown, with each feather having a pale white or pale reddish-brown edge. The shoulder feathers have additional white streaks. There is no wing speculum. The tips of the largest wing coverts and the secondary flight feathers are white, forming two white bands on the wing. The tail feathers are dark brown with pale reddish-brown tips.
Juvenile
Generally resembles the female, but the feathers on the abdomen have grey-brown streaks. Juvenile males have a green speculum.
General Characteristics
- Eyes: Brown, occasionally reddish.
- Bill: Grey or pale grey.
- Legs: Grey-blue or pale black.
Measurements
- Wing (male): 260 – 292 mm, (female): 235 – 266 mm
- Tail: 150 – 228 mm
- Tarsus: 37 – 40 mm
- Bill: 54 – 58 mm
- Weight: (male): 0.75 – 1.15 kg, (female): 0.70 – 0.91 kg
Distribution
This duck species is distributed in the temperate regions of North America, Europe, and Asia. They migrate to the Southern Hemisphere during the winter.
In Vietnam, the species is quite common in the Red River Delta and the Central region during the winter.