Eastern Bluebird

“The eastern bluebird is the only bluebird found east of the Rockies.”

These beautiful and beloved little birds are considered harbingers of spring and in some places, their song can be heard even when snow is still on the ground. Unlike so many other animals, their status is of least concern, and their numbers are actually increasing. This is largely due to the fact that bluebirds have no trouble living around human beings and won’t hesitate to build a nest in a house provided for them. They return the favor by eating insect pests.

Where To Find Eastern Bluebirds

The eastern bluebird is a favorite of birdwatchers because it is conspicuous and generally easy to find. A birdwatcher has the best chance of finding an eastern bluebird in the places where they live year-round. This would be in states found east of the Rockies below the 40th parallel, as far south as West Palm Beach Florida, and as far north as the Cape Cod Peninsula in Massachusetts. People who live north of the 40th parallel can see the bluebird during the spring when it comes to breed. The birds can be found, again east of the Rockies and as far north as Yellowknife in the Northwest Territories and as far east as Nova Scotia.

The eastern bluebird can be seen perching on a fence, on a telephone wire, or may show up as a flash of blue in the grass as it dives after a worm. If it’s the breeding season, the birdwatcher might catch a pair building a nest in a bluebird house, or in a cavity of a dead tree. The bird may even swoop by, singing.

Scientific Name and Evolution

The eastern bluebird’s scientific name is Sialia sialis, which is Greek for “a type of bird.” Eastern bluebirds belong to the genus Sialia. As a result, their closest cousins, which are also part of the same genus, include mountain and western bluebirds. A rung further up the biological ladder reveals these birds to be members of the Turdidae, or thrush family.

Going further we find that all these thrushes are Passeriformes, the largest avian order which contains about 6,500 species – over half of all extant species. Definitive evidence of these birds exists dating back to the Oligocene (23 – 33.9 million years ago). Fossils belonging to this era have been found in Europe, in Germany and Poland, to be precise.

Appearance

The eastern bluebird is about 7 inches long on average, with a 9.8 to 12.6-inch wingspan. The male has a back of pure, bright blue, a rusty breast, and a white belly. They have small beaks and short legs and weigh about an ounce. The female is a little larger, but her plumage is duller. Juveniles are brownish-gray with a bit of blue on the wings and tail. They have spots on their breast that disappear as they mature.

Eastern bluebirds tend to have a hunched look when they perch. The coloration of the juvenile and the female is probably protective and keeps them hidden from predators. Any blue in the plumage comes about when the light strikes proteins arranged a certain way in the feathers, for no bird can create blue pigment the way it can create red or yellow pigment.

Behavior

Eastern bluebirds are gregarious save for the breeding season when a male claims a one- or two-acre territory and defends it. He’ll also defend a feeding territory during the winter. Other than that, bluebirds can form huge flocks. Most of the birds are monogamous during the breeding season. It has been observed that some birds have chicks with more than one mate at a time.

Nesting

The bluebird’s nest is cup-shaped, rather loose, and made of twigs, hair, feathers, or grass. The female does most of the work of building the nest, with the endeavor usually taking about 10 days. She will make the nest in a cavity made by a woodpecker or a house that’s been provided by a human. Bluebirds prefer their nest boxes to be between 2 and 50 feet off the ground.

Migration Pattern and Timing

Migration for eastern bluebirds in the southern part of their range tends not to happen unless food is very scarce. Birds in the northern part of the range fly south during the winter to a specific area in western Texas and northeast Mexico where some populations of eastern bluebirds spend their winters.

Diet

Ornithologists believe that about 68 percent of the bluebird’s diet is made up of insects and other small invertebrates such as snails and grubs. Many of these animals are harmful to plants, so the bluebird’s diet is beneficial to humans. During the colder months when animal protein is scarce, the bluebird will subsist on berries found in the woods. This includes the berries of honeysuckle, which are poisonous to humans. Vegetation sprayed with pesticides is detrimental to bluebirds and was one reason their numbers declined during the middle years of the 20th century.

Bluebirds get their water from ponds and streams and also drink from and bathe in birdbaths. Since they prefer running water to still water, a human might install a device to agitate the water in the birdbath.

Predators and Threats

The eastern bluebird has to cope with a great many predators and threats. Chipmunks, raccoons, flying squirrels, snakes, and domestic cats steal eggs and nestlings. Aggressive sparrows and starlings chase them out of a territory. Fire ants sting nestlings to death and then devour them. Birds of prey such as kestrels, hawks, and owls make meals of both adults and young.

Bluebirds can catch diseases from dirty feeders and baths. Humans need to make sure that feeders and baths are kept clean, for birds can pass such diseases as salmonella, avian pox, and trichomoniasis among each other. Eastern bluebirds can also be plagued by parasites such as lice and blowflies.

Reproduction, Babies, and Lifespan

Eastern bluebirds breed in the spring and summer and usually raise two or three broods a year. The male picks a spot to build a nest and advertises it by flapping his wings and tossing a few twigs into the cavity. After mating, the female builds the nest and then lays from 3 to 7 light blue eggs. She lays one egg a day and then incubates it. They hatch in about two weeks.

The chicks are helpless and fed by both parents. At first, they’re given soft-bodied food such as earthworms, but as they grow bigger and stronger the parents may bring beetles. The chicks are ready to fly the nest after 15 to 20 days and are ready to breed by the next summer.

The eastern bluebird’s lifespan is between six and 10 years, and the oldest known eastern bluebird lived for 10 years and five months. Though the eastern bluebird is long-lived for a little bird, most birds fall to predators and don’t live past their first year.

Population and Conservation Status

Biologists believe that the eastern bluebird population is around 20 million birds. Their IUCN status is of least concern, with their numbers having recovered nicely in areas where pesticides had contaminated their food.