Bluebirds are small, blue-colored perching birds in the thrush family (Turdidae). There are three species of bluebirds in North America. All of these bluebirds nest in natural cavities or nest boxes. They tend to feed from perches, flying down to catch insects as they see them, and sometimes hawking insects in the air.
The eastern bluebird (Sialia sialis ) occurs in shrubby habitats, old orchards, recent clear-cuts and burns, and other open habitats with woody plants in eastern and central North America and south to Nicaragua in Central America. The male of this species has a bright, blue back and a brick-red breast, while the female has a somewhat similar, but more subdued coloration. Northern populations of the eastern bluebird are migratory, wintering in the southeastern United States or further south.
The male western bluebird (S. mexicana ) is rather similar in coloration to the eastern bluebird, but it has a blue throat, and a red shoulder. This species and the mountain bluebird (S. currucoides ) are western in their distributions. The male mountain bluebird is a striking, sky-blue color, and this species tends to occur at
relatively higher elevations than the western bluebird during the breeding season.
Populations of bluebirds have declined greatly in large parts of their ranges. In part, this has been caused by modifications of their habitat by humans, especially agricultural and forestry activities that have reduced the availability of the nesting cavities that bluebirds require. The use of pesticides has also affected bluebirds in some areas.
Bluebirds have also suffered badly from competition for their essential nesting cavities with common starlings (Sturnus vulgaris ), and, to a lesser degree, the house sparrow (Passer domesticus ). Both of these species were introduced to eastern North America from Europe in the later nineteenth century. The common starling is now the most abundant bird in North America, and populations of bluebirds have declined drastically throughout the range of this invasive pest. Fortunately, bluebird populations have been increasing in many areas during the past several decades, although they are still generally depressed. The population recovery of bluebirds has been substantially assisted by volunteer programs that provide these lovely and interesting birds with artificial nest boxes.
See also Thrushes.