South-western and west-central USA (from central California, southern Nevada and extreme south-western Utah) south to north-western Mexico (to southern Baja California and central Sonora). Winters south to west-central Mexico (at least to Nayarit).
Population
Estimated population is 4,000,000 (2010).
Costa's Hummingbird (Calypte costae) [XC132964]
by Paul Driver from Rose Mine Valley, San Bernardino Mountains, San Bernardino, California, United States (call)
Costa's Hummingbird (Calypte costae) [XC552946]
by Paul Marvin from fire info pullout, Laguna Mtns, San Diego County, California, United States (song)
Subspecies
Genus often merged into Archilochus, and both have sometimes been subsumed into Selasphorus. However, in morphology, vocalizations and displays, members of present genus stand apart from the Selasphorus-Archilochus assemblage. Alternatively, present genus sometimes merged into Mellisuga. Some authors would even place present species in the Archilochus superspecies. However, species is closely related to Anna's Hummingbird (Calypte anna). Has hybridized with several other species of western North American hummingbirds, including Anna's Hummingbird (Calypte anna), Broad-tailed Hummingbird (Selasphorus platycercus), Blue-throated Hummingbird (Lampornis clemenciae), Calliope Hummingbird (Selasphorus calliope) and Black-chinned Hummingbird (Archilochus alexandri).
BirdLife International Species Factsheet