It wasn’t that many years ago that the Eastern bluebirds were nearly extinct. This was due to loss of habitat as the lands were cropped with monoculture and also due to the house sparrow introduction. Thanks goes to the many volunteers who worked to build nest boxes and provide habitat for these birds. To lose them from our earth would be tragic.
Bluebirds eat by setting a perch, flying to the ground to eat the insect, then flying back to a perch. Because of this foraging behavior, they like to be in areas that have some openness to them, such as prairies and grasslands. They will usually eat insects in the spring and summer months but will never turn down a mealworm treat!! During the winter, they will eat fruits and seeds.
Jim has maintained a bluebird trail for many years; we call is the Hess Trail. A bluebird trail is simply a number of nest boxes that are monitored monthly. Our trail runs around our property and along Hwy N; to make this weekly checks, Jim rides his bike. We sent our numbers in to the Lafayette County Bluebird Society and to the Bluebird Restoration Association of Wisconsin. Check out the blog article, too.
Along with the references above, the North American Bluebird Society is another place to find answers.