The bluebirds who live here are the mountain bluebird, meaning they are all blue with a white belly. They differ from their relatives, the eastern and western bluebirds who have a bright orange breast. They are a member of the thrush family and are native to North America. At one time they were as common as their cousin, the American robin. Bluebirds require existing cavities for their nests. When this resource disappears, their numbers decline.