Attractively patterned black-and-white swift of the Andes and adjacent Pacific lowlands. Ranges widely as singles and loose flocks, sometimes feeding low with swallows, but more often higher overhead when it can be located by its distinctive, rapid-paced buzzy chatters. Plumage is distinctive: black cap, white underparts (with black belly band in west slope populations), and a white rump. Flight faster than swallows with stiff wingbeats. Like all swifts, only perches at remote nest sites and roosts.