A male bluebird is perched on a cherry tree in spring.
From a conservation standpoint, one of the more interesting things about the bluebird is the fact that it is a secondary cavity nester. This means that it creates its nests in cavities, but is not strong enough to peck out its own holes and is therefore dependent on woodpeckers and other natural cavity creators.
From 1920-1970 there was a major decline in the bluebird population. The bluebird went from being as common as the robin, to being so rare that birders were sure of its inevitable extinction. There were many reasons for the decline, including loss of habitat, pesticide use, weather changes, snag (dead tree) removal, and an influx of house cats. However, the main reason for the population decline was the introduction of the House Sparrow and the European Starling into America, both cavity nesters, both extremely competitive and aggressive.
In 1978 the North American Bluebird Society (NABS) was formed by citizen scientist...