The bright-blue breeding plumage of the male, easily observed on a wire or open perch, makes this species a favorite of birders.

The male's call includes sometimes soft warbles of jeew or chir-wi, or the melodious song chiti WEEW wewidoo.

[4] The eastern bluebird was formally described by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae under the binomial name Motacilla sialis.

[12] The eastern bluebird is found east of the Rockies, southern Canada to the Gulf states, and southeastern Arizona to Nicaragua.

[14][15][16] From 1966–2015 the eastern bluebird experienced a greater than 1.5% annual population increase throughout most of its breeding and year-round ranges, with exceptions including southern Florida and the Ohio River valley.

[18]An isolated, insular subspecies of the eastern bluebird is found on Bermuda, and has a distinctive, brighter blue coloration compared to mainland populations.

However, analysis of fossil strata found no evidence for the existence of bluebirds on the islands prior to European colonization.

Using simulations and molecular evidence, a 2013 study found that the Bermuda bluebirds likely descend from very small founder population from a single colonization event during the 1600s.

It is likely that the alteration to the islands' ecosystem due to the clearing of native forest facilitated this colonization by providing optimal bluebird feeding habitat, along with a lack of predators.

Nests are constructed in trees within abandoned woodpecker holes or other cavities that provide adequate protection (usually several feet above ground).

Natural predators of eggs and nestlings can include eastern chipmunks, flying squirrels, American black bears, fire ants, and raccoons.

Bluebirds of all ages (including adults) are threatened by rat snakes, Eastern racers, American kestrels, and domestic cats.

Non-nesting adults face predation by all native species of falcons, owls, and most varieties of hawks, particularly those in the genus Accipiter.

It has a preference for grasshoppers, crickets, katydids, and beetles; and will also eat earthworms, spiders, millipedes, centipedes, sowbugs, and snails.

Bluebirds feed by perching on a high point, such as a branch or fence post, and swooping down to catch insects on or near the ground.

Clearing forests made new habitat available for bluebirds and nesting sites were created in the increasing numbers of apple orchards and in wooden fence posts that eventually rotted.

However, increasing competition with the invasive species of European starlings (Sturnus vulgaris) and house sparrows (Passer domesticus) along with loss of farmland began to take a toll on bluebird populations.