Where bluebirds fly: How to be a responsible bluebird box landlord

by Saige Sentell, Education Director

“Somewhere over the rainbow, bluebirds fly…” from The Wizard of Oz has been sung for nearly a century, carrying with it an image of beauty, freedom, and hope. For generations, the sight of a bluebird perched on a fence post or gliding over an open field has been a simple joy and a reminder that wildness still lingers close to home. However, there was a time not long ago when the eastern bluebird nearly disappeared from Indiana’s skies.

In the mid-20th century, bluebird populations plummeted across North America. Changes in land use, the clearing of old orchards, the removal of snags (standing dead trees) and fence posts, and the widespread use of pesticides, stripped the species of its natural nesting sites. At the same time, the introduction of European starlings and house sparrows brought fierce competition for the few nesting cavities that remained. By the 1960s, the cheerful song of the eastern bluebird had grown faint in much of the Midwest.

That’s when a self-taught naturalist named Dick Peterson decided to do something about it. Standing on the edges of his Minnesota farmland, he watched as one of his favorite birds struggled to find a place to raise its young. Instead of accepting their decline, Peterson began to experiment with nest box designs, recording every success and failure. After years of tinkering, he perfected what is now known as the “Peterson Bluebird Box,” a slanted, wedge-shaped design with a narrow oval entrance that discouraged starlings and raccoons while keeping the nest dry and cool. Peterson didn’t patent his idea or sell plans. He gave them away freely, sharing instructions with bird clubs, state parks, schools, and anyone willing to build a box and put it up. His generosity sparked a grassroots conservation movement, powered not by large organizations but by thousands of ordinary people who became “bluebird landlords” and created “bluebird trails,” playing a pivotal role in the species’ recovery.

Bluebirds at the Sam Shine Foundation Preserve. Wyatt Downey

The eastern bluebird, Sialia sialis, is a small thrush, slightly larger than a sparrow, and easily recognized by its bright plumage: a brilliant sky-blue back, rust-orange chest, and white belly. Females share the same pattern in softer tones. Their gentle song, often described as a cheerful “chur-lee,” is a familiar soundtrack to Indiana’s spring mornings. Bluebirds are secondary cavity nesters, relying on existing holes, typically abandoned woodpecker cavities or natural hollows in decaying trees. Historically, they found plenty of nesting spots in old orchards and pastures dotted with wooden fence posts, but modern landscapes offer few natural cavities, which is why nest boxes have become essential to their survival. Bluebirds are voracious insect-eaters, feeding on beetles, crickets, caterpillars, and other pests during the warmer months. In winter, when insects are scarce, they switch to berries from native plants such as dogwood, sumac, and cedar.

If you’re ready to join the ranks of bluebird landlords, design matters. Whether you choose the traditional rectangular style or a Peterson box, a few well-tested guidelines make the difference. The entrance hole should be 1½ inches in diameter, small enough to exclude starlings but large enough for bluebirds. Mount the box four to six feet off the ground on a smooth metal pole rather than a tree, which helps deter predators. Face the entrance east or southeast to catch morning sun and shield from afternoon heat. Keep boxes roughly 100 yards apart to avoid territorial conflicts between pairs. Adding a metal baffle below the box can prevent raccoons, snakes, and cats from reaching the nest. In some cases, paired boxes set 10-20 feet apart can reduce competition between bluebirds and tree swallows, which also nest in cavities. The two species often tolerate each other when given adjacent homes, each raising young peacefully.

Putting up a bluebird box is the easy part; being a responsible landlord takes a little more effort. During nesting season, from March through August, boxes should be checked weekly. Bluebirds are surprisingly tolerant of respectful human visits, and regular monitoring helps ensure their safety. Record what you see: the number of eggs, hatchlings, and fledglings, as well as any signs of predators or parasites. This data is valuable not only for your own records but for citizen science programs like the Cornell Lab of Ornithology’s NestWatch which track population trends across the region. Be prepared to remove nests of house sparrows, which aggressively destroy bluebird eggs and young. After each brood fledges, clean the box to remove old nesting material and parasites. At least once a year, typically in late fall or winter, give the box a full cleaning and inspection to make sure it is safe and sturdy for the next season. A well-maintained box can host bluebird families for a decade or more, turning a single structure into a multi-generational home.

Education program participants learned how to make bluebird boxes in September and took them home thanks to the generosity of Loren Wood Builders. Photo courtesy of Loren Wood Builders

Here in Indiana, eastern bluebirds are a year-round resident, but in March they will start inspecting boxes before the trees have fully leafed out. They typically raise two to three broods per year, with each clutch containing four to six eggs. Fledglings take flight about 18-21 days after hatching, often staying nearby as their parents prepare for another nesting attempt. By late summer, family groups and juveniles form loose flocks that linger through fall, feeding on insects and ripening berries. Some bluebirds migrate short distances south, but many remain in Indiana through winter, especially during mild years. They will roost together in boxes or natural cavities to conserve warmth, a reminder to leave your boxes up year-round, offering shelter from cold winds and snow.

While nest boxes are vital, true bluebird conservation depends on healthy, connected habitats. Sycamore Land Trust’s restoration projects, from replanting native prairie grasses and wildflowers to managing invasive species, create the open, insect-rich environments bluebirds need. Volunteers who build and monitor bluebird boxes often pair those efforts with native landscaping by planting serviceberry, red cedar, and winterberry for food and cover. In doing so, they also support a cascade of other species, from pollinators to small mammals to the hawks that hunt over restored grasslands.

The story of the bluebird’s comeback is a story about connection, between people and wildlife, between backyards and nature preserves, between small acts and lasting change. What began as one man’s design on a Minnesota workbench has grown into a continent-wide movement powered by volunteers, families, and conservationists like those in Sycamore’s community. When you hear that familiar lyric “Somewhere over the rainbow, bluebirds fly,” remember that here in southern Indiana, they already do. Their bright wings flash over restored wetlands and meadows, a living symbol of renewal and of what’s possible when people come together to give nature a helping hand.

This story was featured in the Fall 2025 issue of The Twig, “The Citizen Science Issue.” Read more at sycamorelandtrust.org/twig.