Laura Erickson's For the Birds

This lovely little bird is easy to see at feeders, but even easier to detect because of the unique high-pitched trill made by the male’s wings in flight. The feather tips that produce this sound wear down by winter; the male molts into fresh, noisy feathers on his Mexican wintering grounds so he’ll be plenty loud come the breeding season.

This species breeds in high mountain meadows up to over 10,000 feet in elevation. Females build very thick nests to provide some insulation during freezing nights; males fly upslope to sleep out of the worst pockets of frozen air. Like Rufous Hummingbirds, this species is extremely pugnacious at feeders, often driving away much larger species.