The Torrent Duck (Merganetta armata) is a monotypic Andean endemic specialist of cold mountain streams. Six races are recognized in mountainous regions from w. Venezuela to c. Chile and w. Argentina. Sexually dimorphic, males show considerable geographic variation in head patterning whereas females appear similiar throughout their range.
Torrent ducks are the only waterfowl that inhabit the turbulent Andean streams, and are impossible to confuse with other species (Johnsgard 1978).
Adult males are characterized by a bold black and white head pattern and a brownish-grey body, wings and tail. The face is white, with the eyeline extending down the next to the upper breast and connected to the npe by another black stripe (Gomez-Dallmeier and Cringan 1989). The upperparts are mostly made up of gray to blackish feathers with pale gray to white margins, while the flanks and underparts vary from predominantly white with small black spotting (northern forms) to mostly blackish with brownish feather margins (southern forms) (Johnsgard 1978). Adult females are greyish dorsally and on the head and neck, but have finely vermiculated feathers in the eyeline area that extends down the side of the nexk and along the side of the body. Both sexes have an iridescent-green speculum (Gomez-Dallmeier and Cringan 1989).
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In both sexes the bill is bright red, the legs and feet are reddish with darker markings, and the iris is brown (Johnsgard 1978).
From Johnsgard 1978.
Folded wing 142-84 mm, Culmen 29-31 mm., Weight 440 g.
Folded wing 132-65 mm., Culmen 25-27, Weights 315-400 g.
Johnsgard's morphometrics (taken from Niethammer 1952) contrast with those provided below by Gomez-Dallmeier and Cringan 1989).
Length 410 m, Wing 143 mm, Weight 315 g.
Length 427 mm., Wing 150 mm., Weight 307.