All bluebirds are pest insect eaters from the time they hatch until they expire with about 70% of their diet beomg insects. However, with some variation among the species and the area bluebirds will include fruits and berries sometimes up to 30% of their diet.
The diet of young bluebirds is composed entirely of insects to give the youngster the maximum amount of protein during the 17 days they remain in the nest. Eastern bluebirds eat ants, beetles such as the Colorado potato beetle; Mexican bean beetle and cucumber beetles, May beetles, weevils, grasshoppers, crickets and caterpillars as adults and feed the same diet to their young. Eastern bluebirds also consume centipedes and sowbugs and unfortunately they consume spiders and many of the other beneficial insects, but it all balancces out in nature.