Mountain bluebirds (Sialia currucoides) have returned to the lower areas in Rocky Mountain National Park, a sure sign that spring is here. Soon broad-tailed hummingbirds (Selasphorus platycercus) and a myriad of spring wildflowers will arrive, although frosts and snowstorms are still a real possibility. Springtime in the Rockies is a time of unpredictable weather as well as great beauty.
Mountain bluebirds are small blue birds (male) or grayish brown birds with blue tinge on tail and flight feathers (female) that nest in cavities. At one time, modern forestry practices that emphasized removing dead trees or those with cavities drastically reduced the number of homes available for these lovely birds in many areas. Fortunately national parks emphasize the importance of the full range of natural processes including leaving dead and dying trees in place unless they present a clear danger to human safety. The result is that there are large numbers of attractive nesting cavities in the park for the bluebirds to call home.
Mountain bluebirds are members of the thrush family, and like many of their relatives, they eat insects that they capture on the wing or on the ground. They prefer to perch on fences, trees and shrubs surveying broad open areas for their next meal. They migrate north starting around March and are distributed as far north as Alaska and as far east as Manitoba. In the late fall they migrate south to the southern US and into Mexico.
Rocky Mountain National Park also has numbers of western bluebirds, and occasional reports of eastern bluebirds, so you may be able to see all three varieties on your next visit to the park. You may want to visit USGS Patuxent National Wildlife Research Center's descriptions of mountain bluebirds, western bluebirds, and eastern bluebirds to understand the differences among these birds in more detail.