Eastern Bluebirds spend the winter in the southeastern United States and return to the upper midwest to breed in early March. Immediately after they arrive, the males begin looking for nesting sites in tree cavities or in nesting boxes built for them by birdwatchers.
Males try to attract females to the sites they have chosen by singing and flapping their wings and placing nesting material inside. The female makes the final decision. Once she has chosen, she spends a week or so bringing in soft, dry grass to make a deep, cup-shaped nest. She then lays a clutch of three to six eggs, and for the next two weeks, she incubates them.
Once hatched, the nestlings remain in the nest for about two weeks. Both parents feed the young. After the fledglings have left the nest, the breeding pair usually raises another brood, sometimes two, during the nesting season. They head south to their winter home in late September.
Bluebirds hunt for food in an unusual way. They perch on tree branches to spot insects on the ground and then flutter down to catch them, often hovering to pick them up rather than landing. They feed on a wide variety of insects, including crickets, grasshoppers, and beetles, and occasionally on spiders, earthworms, snails, small lizards, and tree frogs. They also eat berries, especially in the fall.
Sparrows compete with bluebirds for nesting sites. They will take over the sites, smashing eggs, killing young, and sometimes killing adults. To prevent sparrows from taking over your bluebird box, staple strips of shiny metallic tape nearby. As the strips flutter in the breeze, they scare away the sparrows, but not the bluebirds.
My Dad lives in Caro, MI and is surrounded by farm fields. For Christmas one year, we made him a blue bird house from the official plans from the North American Blue Bird Society The very first year, bluebirds moved in and were a lovely garden companion. We made him another bluebird house the following year and sure enough - it was also occupied. He had to hang Mylar strips near the house to keep the sparrows away but it worked like a charm and he now hosts two pairs each spring. We've just hung our first house here in Northern Michigan, on the edge of the woods and we're hoping a resident bluebird finds it and moves in.