[3][4] It has a western breeding range mainly from California to British Columbia, and migrates to the Southwestern United States, Mexico, and Central America for its wintering grounds.

[3] When an adult male is competing for territory or females, the dark red feathers of its gorget distend outwards to create a more distinct appearance.

[3][4] Open montane forest, mountain meadows, and willow and alder thickets may variously serve as breeding grounds.

[4][5] These birds feed on nectar from flowers using a long extendable tongue, drink sap from holes created by sapsuckers or catch insects on the wing.

[8] The humming sound derives from aerodynamic forces generated by both the downstrokes and upstrokes of the rapid wingbeats, producing acoustic oscillations and harmonics.

[3][9] The male then ascends temporarily to 20 m (66 ft) and dives at high speed, with the rapid descent causing sonation of wing and tail feathers combined with vocalization, intending to attract attention of the female.

[9] Research in a wind tunnel demonstrated that the male courtship display includes sounds produced by three independent feather or vocal components, each with different acoustic characteristics, thus potentially containing different messages appealing to the female.

[11] As the smallest North American hummingbird species, calliopes appear to adapt their relatively higher surface-to-volume ratio to improve convective cooling from air movement by the wings.

[11] All hummingbirds dissipate heat partially by exhaled air, and from body structures with thin or no feather covering, such as around the eyes, shoulders, under the wings (patagia), and feet.

[4] As this species has a restricted wintering range in Mexico and travels an exceptional migratory distance annually of up to 9,000 km, it is on a watchlist for factors that could diminish the population.