The calliope hummingbird ( ; Selasphorus calliope) is the smallest bird native to the United States and Canada.
It was previously considered the only member of the genus Stellula (meaning little star), but research evidence suggests its existing placement in the genus Selasphorus. The bird was named after the Greek muse Calliope.
Description
thumb|Male calliope hummingbird with its purple gorget (neck) feathers slightly extended
The calliope is the smallest breeding bird found in Canada and the United States.
Calliope hummingbirds have glossy green on the back and crown with white underparts. Females and immatures have a pinkish wash on the flanks, dark streaks on the throat and a dark tail with white tips. The only similar birds are the rufous hummingbird and the Allen's hummingbird, but these birds are larger with more distinct and contrasting rufous markings on the tail and flanks, and longer central tail feathers.
thumb|Female feeding insects to chicks
Habitat and distribution
The breeding habitat of calliope hummingbird is varied among open shrub habitats and altitudes. Nesting usually occurs at higher altitudes in the Rocky Mountains. Nests have been observed from as low as in Oregon and Washington elevation to the tree line at over . Humming serves as an audible communication to alert other birds of the arrival of a fellow forager or potential mate. 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. Male calliope hummingbirds also make visual displays to females and nearby males by extending their purple gorget feathers to appear larger. 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. While hovering, calliope hummingbirds do not benefit from the heat loss by air convection during forward flight, except for air movement generated by their rapid wing-beat, possibly aiding convective heat loss from the extended feet.
Status
As of 2019, calliope hummingbirds have a relatively stable breeding population of about 4.5 million. The calliope hummingbird may be aggressive in its territory with other hummingbird species and birds, including Gray Flycatchers, American Robins, and Red-tailed Hawks.