He continues this training phase for several days after they leave the nest. While the male is busy with the fledglings, the female remodels the old nest or builds a new one for a second brood. In the yard and around the garden, bluebirds consume grasshoppers, flying insects, beetles, and caterpillars. They also eat berries and fruits found near their nests, especially during the winter when insects are scarce. During the last 60 years, bluebird numbers have decreased 90 percent in the eastern United States.
Severe winters increase winter mortality.
Changing agricultural practices create well-trimmed orchards with no cavity trees for nest sites. Exotic species competing for remaining nest sites make nesting even more difficult. Helping Bluebirds Finding suitable nest sites is perhaps the most severe problem the bluebird faces today. Allowing trees to mature and develop natural cavities takes too long. A much quicker solution is to provide man-made wooden nest boxes.