About Mergus merganser Linnaeus, 1758
This species measures 58–72 cm (23–28+1⁄2 inches) in length, has a 78–97 cm (30+1⁄2–38 inch) wingspan, and weighs 0.9–2.1 kg (2 pounds 0 ounces – 4 pounds 10 ounces). On average, males are slightly larger than females, though their size ranges overlap. Like other species in the genus Mergus, this bird has a crest of longer head feathers, but these usually lie smoothly rounded behind the head and do not normally form an erect crest. Adult males in breeding plumage are easily recognizable: their bodies are white with a variable salmon-pink tinge, their heads are black with an iridescent green sheen, their rumps and tails are grey, and their wings are largely white on the inner half and black on the outer half. Females and males in eclipse (non-breeding plumage, from July to October) are largely grey, with a reddish-brown head, white chin, and white secondary wing feathers. Juveniles of both sexes are similar in appearance to adult females, but also have a short black-edged white stripe between the eye and bill. The bill and legs range from red to brownish-red; this color is brightest on adult males and dullest on juveniles.
