Anna's Hummingbird (Calypte anna) is a medium-sized hummingbird native to the west coast of North America. Anna's Hummingbirds are found along the western coast of North America, from southern Canada to northern Baja California, and inland to southern Arizona. They tend to be permanent residents within their range, and are very territorial.
Anna's Hummingbirds are the only hummingbirds to spend the winter in northern climates; they are able to do this as there are enough winter flowers and food to support them. During cold temperatures, Anna's Hummingbirds gradually gain weight during the day as they convert sugar to fat. In addition, hummingbirds with inadequate stores of body fat or insufficient plumage are able to survive periods of sub-freezing weather by lowering their metabolic rate and entering a state of torpor.
Unlike most hummingbirds, the male Anna's Hummingbird sings during courtship. The song is thin and squeaky. During the breeding season, males can be observed performing a remarkable display, called a display dive, on their territories. When a female flies onto a male's territory, he rises up approximately 30 metres before diving over the recipient..
Source: en.wikipedia.org/wiki/Anna's hummingbird - 09.10.2010