By Dennis Prichard
Spring brings some really wonderful days of warm weather with clear blue skies, fresh green growth, renewed activity in all of nature and, of course, bluebirds. In fact, we have termed such idyllic days as just that – Bluebird Days!
There are three species of bluebirds in North America. The Eastern bluebird is probably the most familiar since it resides where most of the continent’s human population lives, east of the Mississippi River. These birds are a navy blue on most of their bodies with a splash of reddish hue on their breast and throat and a white belly.
The Eastern bluebird look very similar to their cousins, the Western bluebirds, whose reddish pattern extends over their upper back. Birders argue among themselves over the identity of these species where they overlap in the Plains states down into Texas.
A third species is more easily identified. It is the Mountain bluebird. This bird is more of a sky-blue all over with white under the tail. Its range is similar to the Western but tends to prefer higher elevations, thus the name. I happen to be lucky enough to live in an area of the country that hosts all three species of bluebirds at some time of the year. (Try to guess where if you are a birder!)
Bluebirds are cavity nesters, that is to say they make their nests in holes of old tree branches. They prefer these holes to be four to five feet above the ground, but will make do with varying heights. What they can’t compromise on is the size of the hole and its corresponding cavity where the nest will be. Abandoned woodpecker holes suffice for this, but competition for housing is fierce.
Introduced European starlings are more aggressive and will actually clean a cavity containing bluebird eggs to replace them with their own. Then there are nest-parasites such as cowbirds that lay their eggs in the bluebird nest and promptly leave so that the bluebirds will raise the youngster just like one of their own. This larger chick usually gets all the food, pecks the bluebird chicks to death, or pushes the smaller ones out of the nest. No bluebird chicks are produced, only cowbirds.
Another setback occurred when wooden fence posts were replaced with modern steel ones. The rotting wooden posts were the perfect height for the bluebirds, and woodpeckers gave them the right cavities to use – steel posts just wouldn’t do. So a double-whammy was unleashed on the pretty birds.
Along comes the North American Bluebird Society (yes, there is such an organization) to help turn this tide. They perfected plans for the right kind of box to house the nest. The hole has to be just the right size to fit a mother and father bluebird, but too small for starlings and cowbirds. This hole should be deep enough at the entrance to keep prying raccoon paws from reaching in. Adequate drainage assures spring rains will not accumulate inside. Then this box is attached to the steel fence posts in an area where open fields provide plenty of visual distance and an abundance of insects. These boxes should be placed far enough apart to lessen competition between nesting pairs, but maximize brood production. Usually no closer than 100 feet is a good rule.
Bluebird numbers were getting alarmingly low from the 1950s to the turn of the century, but with the help of human friends the numbers are coming back. It is very easy to put up and maintain bluebird houses – just clean them out before each nesting season and let the birds do the rest. It is also fun to see them return to nest year after year and bring us those Bluebird Days!
For more information on bluebirds and building their nest boxes, visit the North American Bluebird Society’s webpage.
Dennis Prichard is a retired park ranger. He’s worked and studied wildlife at many National Parks and Wildlife Refuges including Carlsbad Caverns, Mammoth Caves, the Everglades, Sequoyah NWR in Oklahoma, Sevilleta NWR in New Mexico, and Isle Royale National Park, to name a few. He travels in a fifth wheel with his wife and dog, a Labrador named Cricket.