A small diving duck. Males are black and white, while females have red-brown heads; some birds visit Britain in autumn and winter.
Males have white plumage with black markings, while females have red-brown heads.
Winter smew meals differed between nearby waters in the Netherlands. In Lake Yssel, smelt accounted for about 96% by number of 996 fish reconstructed from stomach and gullet remains. Perch made up about 3%. Smelt dominated the fish eaten in this lake.
Of 21 birds examined in January–March 1977, 12 came from Lake Yssel. All four birds from nearby Ketelmeer contained perch. Smelt were practically absent from that lake; other prey included ruffe and pike. Fish species and sizes were identified from otoliths, small hard structures, and bones remaining in the digestive tract. Across the sampled waters, 67% of fish belonged to the 5 and 6 cm length classes. Underwater, smew caught small fish whose species varied between waters.
An extinction-risk assessment has not been added yet.
Kyoto Prefecture’s 2026 Red Data Book identifies habitat deterioration associated with river engineering, declining water quality and recreational activities as threats. Few smew winter in the prefecture. The recommended conservation measure is a detailed assessment of their wintering habitats.