Fork-tailed Swift

Apus pacificus

Also known as: White-rumped Swift, Pacific Swift

20 cm (8") Accidental. Asian visitor to outer Aleutians and Pribilofs.

Large dark swift with a white throat and forked tail.

In flight; shows conspicuous white rump

The similar Common Swift, another stray from Asia, lacks the white rump.

Was called White-rumped Swift.