Slightly smaller than Eider. Male at close range unmistakable. At a distance the black back is diagnostic. Female similar to female Eider, but feathering on bill is not reaching nostrils, giving the bird a peculiar "smile". Head shape is less triangular with a steeper forehead, and nail of bill is black. V-shaped barring on flanks.

Male: Calls similar to Eider but easily distinguished by the vibrating quality. A "aaaooooooh" (shorter in duration than Eider) Starting on a low note, slowly ascending and ending on a descending note with a distinct vibrato/pulse. Often in the form of three calls: "oohh, a-ohhh hahahaoohohohoh". Usually accompanied by the female "ga ga ga ga".

Display-calls:

Wikipedia: map (se also Xeno-canto below)

Birdlife ecology

Observation.org Latest observations

Video IBC

Image search Flickr NB! May give other species

Sound search at Xeno-canto

Sounds:Recorded by Andrew Spencer,http://www.xeno-canto.org ,CC license