Lesser Scaup | Aythya affinis

Voice

Effectively silent here. Displaying drakes give a thin, soft whistle, whee-oo, that carries barely ten metres over open water; females a hoarse low kerr on take-off. Nothing you will hear while scanning a winter flock.

Identification

The drake has a black head glossed purple in good light, a black breast, a grey back with fairly coarse vermiculation and dingy white flanks finely barred grey. The crown peaks towards the rear, giving an angular nape and a short-necked look. The blue-grey bill carries a small, narrow black nail. Females are warm brown with a sharply defined white blaze at the bill base and often a faint pale ear-spot; eclipse drakes are dark brown with traces of vermiculation on the flanks.

Confusion species

Scaup and Tufted Duck are the comparison. On Lesser Scaup the highest point of the head lies behind the eye, on the rear crown; on Scaup the peak sits over or in front of the eye and the crown runs round. The purple rather than green gloss flips with the light and should only ever confirm, never decide. The wing bar settles it: white across the secondaries, then changing abruptly to grey through the primaries, where Scaup carries white well out into the inner primaries. Tufted Duck has a black back, a tuft or nape bulge and a broad black bill nail. With females the trail goes cold. Female Tufted Duck can show a white bill base too, and Tufted Duck x Pochard hybrids mimic both head shape and back colour; only the open wing then remains, and without it a claim should stay open.

Habitat

Deep fresh waters: reservoirs, gravel pits, park lakes and sheltered harbour basins, diving for zebra mussels, snails and insect larvae. Birds that reach the coast sit with Scaup over shallow sandy bottoms.

Range and movements

Breeds across North America from the prairie potholes to Alaska and winters from the Great Lakes to the Gulf of Mexico. In Europe a vagrant, near-annual since the late 1980s: most in the British Isles, with a disproportionate share on the island of Ireland, where birds stay long, and a few along the North Sea coast; in Iberia mainly in the Canary Islands and the north-west, November to March and almost always drakes. That increase says more about what birders look for than about the bird itself.

How and when to look

Between December and March work a reservoir or gravel-pit flock of Tufted Ducks head by head; in the Canaries the reservoirs and irrigation ponds of Gran Canaria and Tenerife are the places, where birds have stayed for weeks on end. Look for the angular rear crown and the greyer flanks, then wait for a wing-flap or a flight: only with the spread wing in view is the identification finished.

Conservation status

Not globally threatened, but the North American population has fallen from roughly seven million in the 1970s to about three million. Loss of prairie wetlands, poorer condition of females on spring migration and the build-up of selenium and other contaminants are the usual explanations. For the handful reaching Europe the practical risks are lead shot and disturbance on recreational waters.

Scientific name

Aythya affinis | (Eyton, 1838)

Eyton described the species in 1838 as Fuligula affinis; because it was later moved to another genus, the author and year stand in brackets. The genus Aythya was introduced in 1822 by Boie. Aythya is from Greek aithuia, an unidentified diving seabird mentioned by Aristotle and Hesychius. affinis is Latin for 'related to', after the close resemblance to the greater scaup. The specimen the first description was based on came from North America.