Audubon Birds 500 piece Puzzle of the beautiful Bluebird Blossoms is a favorite of many people; sighting the brilliantly colored male in spring is a welcome relief from the dreary northeastern winter. Bluebirds nest in tree cavities, fence posts and, recently, bird boxes, on open farmland with scattered trees. Uncommon for many years, the Eastern Bluebird in making a comeback, at least in part because of nestbox programs. The unmistakable voice of the bluebird in flight is a melodious warble or chur - lee. Bluebirds range east of the Rockies from Southern Canada to the Gulf of Mexico. They are often seen perched on fence posts, from which they drop down to the ground to catch insects. Their diet consists of small fruits and berries, especially in the winter.