In the Wild
When left to their own resources, eastern bluebirds consume 80 percent of their diet in the form of insects such as grasshoppers, crickets, caterpillars, spiders and beetles. Additionally, they will eat wild fruit or berries to make up the difference. Because of this diet, you must employ a bit of creativity when trying to attract these lovely birds to their yard.
Mealworms
Eastern bluebirds love live mealworms. These worms can be purchased at most pet stores and bait shops. Strategically place the live worms on a platform feeder, in your yard near a wood-line where you've observed bluebirds or near a potential nesting site.
Suet
Suet is made by combining ingredients in a base of animal fat such as lard or tallow. To attract bluebirds it is advantageous to combine suet with mealworms. The addition of peanut butter can also add a curiosity factor. Basic suet recipes typically include animal fat, stone-ground cornmeal, peanut butter and mealworms. Crumble firm suet onto your platform feeder with mealworms for your best chance of enticing bluebirds.
Fruit
Because these birds do consume a small part of their diet in the form of fruit and berries, place dried fruit tidbits on your feeder to broaden your chances of attracting these discriminating eaters. Choose fruits similar to ones they might encounter in nature such as blueberries, strawberries, currants and raisins.
Foraging
Birds are natural foragers. Beautify your yard and provide a natural food source by choosing plants that bluebirds prefer; these plants would include American elderberry, foster holly, eastern red cedar and flowering dogwood. Be sure to include varieties that retain fruit into the winter months to provide an ongoing food source.
Nesting
While bluebirds are incubating eggs, the male will often feed the female so she doesn't have to leave the nest. After the chicks hatch, both parents undertake the task of feeding their young until they are weaned. The male will often continue to feed the chicks while the female builds the second nest of the season.