Adult Male:
- Summer Plumage: Head, crest, and upper nape are iridescent black with a purplish sheen. The remaining upperparts, including the shoulders and axillaries, are blackish-brown; scapular feathers have slightly rufous edges. The breast is black. The belly and flanks are white. The undertail coverts are pale black. Primary flight feathers have pale black outer webs and brown inner webs. Secondary flight feathers are white with black tips, forming a white speculum bordered with black. The tail is pale black.
- Winter Plumage: Chin, throat, and lower breast have white streaks. Flanks are pale brown, and the crest is short.
Adult Female:
- The crest is short. Head, neck, back, breast, flanks, and wings are dark brown. Shoulders and flanks are tinged with pale rufous. A narrow white stripe is present on the speculum. The belly is white, slightly tinged with pale brown. The eyes are yellow. The bill is grayish-blue. The legs are grayish-blue with black joints and webbed feet.
Measurements:
- Wing Length: (Male) 189-210 mm, (Female) 185-203 mm;
Tail Length: 49-58 mm;
Tarsus Length: 33-37 mm;
Bill Length: 37-44 mm. - Weight: (Male) 0.55-1.40 kg, (Female) 0.53-1.05 kg.
Distribution:
The distribution of this species encompasses most of the temperate regions of Europe and Asia. In winter, they migrate to North Africa and parts of southern Asia, as far as Malaysia.
Occurrence in Vietnam:
This species is found in the central region of Vietnam.