Anna’s Hummingbirds (Calypte anna) are year-round residents of the western United States and are California’s most common hummingbird. Both sexes are known for their iridescent emerald feathers and males also sport brilliant magenta heads. Unlike many hummingbird species that travel along north/south migratory routes, Anna’s Hummingbirds either remain in one location all year or migrate short distances. They’re feisty little birds and will aggressively defend their feeding territories. These birds are not only beautiful but also tough, resourceful, and surprisingly vocal, often sing complex songs. Listen to a Haikubox recording.
A newly published study demonstrated that feeders are driving evolution among California’s Anna’s Hummingbirds: they are expanding their range northward and changing their beak morphology. The changes began after WWII when eucalyptus trees were widely planted and hummingbird feeders became abundant. The research team reviewed Audubon Christmas Bird Count data (community science!) during this time period to note the birds’ expanding range. They also compared museum specimens to today’s birds to identify beak changes: where feeders are dense, males now have pointier and sharper beaks which can be an advantage during feeder battles. Birds in northern areas have shorter and smaller beaks which allow better heat conservation in cold weather.