Anna’s hummingbirds (Calypte anna) are small, migratory birds that breed in western North America. They are known for their iridescent green and pink feathers, and their ability to fly backwards and upside down. Anna’s hummingbirds are also one of the few hummingbird species that can survive in cold climates, thanks to their ability to enter torpor, a state of hibernation that allows them to conserve energy. During torpor, their body temperature drops, their heart rate slows, and they breathe less often. This allows them to survive on very little food and energy, and to withstand cold temperatures that would be fatal to other birds.
Anna’s hummingbirds typically spend the winter in coastal areas of California and Oregon, where they can find food and shelter from the cold. They often roost in trees or shrubs, and they will sometimes build nests in abandoned birdhouses. During the winter, Anna’s hummingbirds primarily eat nectar from flowers, but they will also eat insects and spiders. They will also drink water from puddles or streams.