Introduction

Once nesting only on the Pacific slope of northern Baja California and California north to the San Francisco Bay area, Anna’s Hummingbird has expanded its range dramatically since the mid-1930s. It now breeds north to Vancouver Island, British Columbia, and eastward to southern Arizona, and it has nested at least once in Texas. This species’ effective use of widely cultivated urban and suburban exotic plants has contributed to its increased numbers and expanded range.

Male Anna’s Hummingbirds attract attention through their elaborate Dive Displays, in which they may ascend 40 meters and then plummet toward their target—a female Anna’s Hummingbird or other bird. Males sing more conspicuously than any other North American hummingbird, and their songs are learned and complex, unusual in nonpasserine birds. They move their head frequently as they sing, flashing the brilliant iridescence of their rose gorget and crown. They are intolerant of other hummingbirds, and chases are frequent.

Female Anna’s Hummingbirds, less conspicuous than males, sometimes defend feeding territories but usually away from those of males. They associate with males only long enough to copulate. The female constructs the nest, incubates the eggs, and cares for nestlings, typically in winter and early spring, timed according to the availability of nectar and small insects for food.

Anna’s Hummingbirds are readily attracted to feeders, which undoubtedly contributes to their abundance in residential areas. In many localities this species is present throughout the year, although it is rarely known if the nesting birds are resident or if they are replaced by individuals from another region.