Vaux's Swift

Vaux's Swift is the smallest swift in North America and the western ecological counterpart of the Chimney Swift, sharing the same stubby, cigar-shaped silhouette, stiff bowed wings, and near-constant flight. It is sooty brown overall, slightly paler on the throat and rump than Chimney Swift, though the two are very difficult to distinguish in the field.

It historically depended on large hollow trees in old-growth conifer forest for nesting and roosting, and large migratory flocks are famous for swirling into big chimneys—such as at school and factory sites—at dusk during migration.

Key field marks

• Tiny, cigar-shaped body, stiff bowed wings, short square tail
• Sooty brown overall, slightly paler throat and rump
• Smaller than Chimney Swift, with a faster wingbeat

Similar species

• Chimney Swift: very similar but slightly larger and darker; ranges mostly separate (Vaux's in the West, Chimney Swift in the East), with limited overlap.
• White-throated Swift: larger, with a bold black-and-white pattern and a longer, more forked tail.

Range and habitat

Vaux's Swift breeds in mature and old-growth coniferous forest of the Pacific Northwest, from southeastern Alaska and British Columbia south through Washington, Oregon, and northern California, with additional resident populations in Mexico and Central America.

Migration

Northern populations migrate through the western US to winter in Mexico and Central America; large communal roosts form at traditional chimney sites during migration.

Behavior

Forages continuously on the wing, often in loose flocks, and roosts communally—sometimes in the thousands—in large hollow trees or chimneys during migration.

Voice

High, thin, twittering chip notes given in flight, similar to but slightly higher-pitched than Chimney Swift.

Feeding

Exclusively flying insects caught in mid-air.

Nesting and breeding

Nests in hollow trees (historically old-growth conifers) or occasionally large chimneys, building a small twig nest glued in place with saliva. The female incubates 3-6 eggs for about 3 weeks.