The diet of the eastern bluebird consists mostly of insects and other invertebrates, including beetles, caterpillars, grasshoppers, spiders, and occasionally earthworms and snails (3) (4) (5). It will even sometimes catch larger prey such as shrews, salamanders, lizards, snakes and frogs (2) (3) (4). In autumn and winter, the eastern bluebird becomes more dependent on small fruits and berries, such as mistletoe, blueberries, currants and honeysuckle (2) (3) (4) (5).
The eastern bluebird typically hunts from a low perch, scanning the ground for prey before dropping down from the perch to capture it (2) (3) (4) (5). It may also catch insects in the air (3) (4), and perches on bushes and trees to feed on fruits (2) (3) (4).
In winter, the eastern bluebird may form small flocks to forage (2) (5), but during the breeding season a pair will aggressively defend a territory (2), even attacking other species that might compete for nesting holes (4). Most breeding takes place in April, but the breeding season may run at any time from February to September (2).
Male eastern bluebirds display at potential nest sites to attract a female, taking nest material to a suitable hole, going in and out, and perching above it while waving the wings. However, the female alone builds the nest and incubates the eggs (4) (5). The eastern bluebird typically nests in a natural tree cavity, an abandoned woodpecker hole or an artificial nest box, in which the female constructs a loose cup of grass and pine needles, lined with fine grass, hair or feathers (2) (4) (5). In areas where nest boxes are common, a female may build a nest in each available hole, but usually ends up using only one (4).
The female eastern bluebird lays a clutch of 2 to 7 pale blue eggs (4) (5), which are incubated for around 11 to 19 days (2) (4). Both adults feed the young (2) (5), which fledge at about 17 to 21 days old (4). This species often has more than one brood each year (2) (4) (5), with the young from later broods often staying with the adults over winter, forming family groups (4) (5).
The eastern bluebird starts breeding from a year old (2) and may live for up to six or seven years in the wild, or for over ten years in captivity (2) (4). This small bird may be taken by a range of predators, including snakes, bears, raccoons, birds of prey, chipmunks, squirrels and domestic cats. Nestlings may fall victim to introduced, non-native fire ants (Solenopsis invicta), which also predate the insects on which the eastern bluebird depends (2).