Adult:
The dorsal surface, wings, and tail are a light brownish-black, with the back, upper tail coverts, and wing coverts exhibiting a slight steel-like sheen. A broad white band runs across the flanks. The feathers on the body have more or less brownish-black streaks. The chin and throat are pale white, with very fine black streaks on the feathers. The remaining feathers on the ventral surface are brown with white edges, and a darker band near the tips. Eyes are dark brown. The beak is black. Legs are pinkish-brown or reddish-black.
Measurements:
Wing: 168-195 mm; Tail: 72-81 mm; Tarsus: 10-11 mm; Bill: 7 mm.
Distribution:
The White-rumped Swift ( Chim ) nests in Mongolia, the Baikal region, Amur (USSR), Northern China, and Japan. In winter, it migrates south to Assam, Burma, Southern China, Indochina, Malaysia, and Australia.
In Vietnam, this species is present during the winter in coastal regions such as Ha Long Bay, Cat Ba Island, Phan Rang, the coast of Southern Vietnam, and Con Lon.