Adult Plumage:
Breeding Plumage: The plumage from the forehead to the nape of the neck is velvety black. The back is pale ash gray, slightly darker on the upper back. The primary flight feathers are dark gray-brown, with pale gray edges on the inner vanes. The secondary flight feathers are silver-gray on the outer vanes, transitioning to dark gray-brown and pale gray edging on the outer vanes of the subsequent feathers, gradually becoming gray. The chin and sides of the throat are almost white. The throat and the front of the neck are slightly gray, transitioning to black on the belly and the posterior flanks. The under-tail coverts and underwings are white. The armpits are pale gray.
Non-Breeding Plumage: The forehead, crown, sides of the head, neck, and entire belly are white. There are black and white streaks on the crown. The nape and a line through the eye are black. The back is pale gray. The eyes are brown. The beak is red. The legs are pale or dark red.
Measurements:
- Wingspan: 220 – 240 mm
- Tail length: 78 – 82 mm
- Tarsus length: 21 – 22 mm
- Beak length: 26 – 32 mm
Distribution:
This species is distributed in China and Indochina. In Vietnam, this species is common during autumn along the central coast (Thừa Thiên and Quảng Trị).