The three species of North American bluebirds—Eastern, Western, and Mountain—are secondary cavity nesters, meaning they cannot excavate their own nesting holes. Their reliance on pre-existing natural cavities has been complicated by habitat loss and competition from non-native species like the European starling. Providing a well-placed, human-made nesting box promotes successful reproduction and population growth. However, the selection of the correct location and mounting setup is paramount to ensuring the safety and successful use of the structure.
Determining Optimal Mounting Height
The height at which a bluebird house is mounted balances accessibility for the birds and protection from ground-level predators. Most bluebird organizations recommend placing the bottom of the nesting box roughly four to eight feet off the ground. This range provides a compromise that suits the bird’s preferences and allows for easy monitoring by the human caretaker.
Mounting the box below four feet significantly increases the risk of predation from animals like raccoons, snakes, and domestic cats. Conversely, positioning the box above eight feet complicates the necessary weekly monitoring and cleaning routines. The ideal height ensures the entrance hole is inviting to the bluebirds and manageable for regular inspections. The primary consideration is keeping the nesting cavity out of easy reach of terrestrial threats.
Ideal Habitat and Landscape Placement
Bluebirds prefer open, short-grass environments where they can easily spot insects on the ground from a low perch. Ideal locations include pastures, large lawns, orchards, and the edges of golf courses or cemeteries. These areas provide the expansive foraging space bluebirds require for feeding their young.
It is generally recommended to avoid placing bluebird houses in densely wooded areas or thick shrubbery. These environments are favored by competing cavity nesters, such as the aggressive house wren, which often harass or destroy bluebird nests. Locate the box at least 50 yards away from heavy brush or deep forest edges to reduce this competition.
The house should be situated in a spot with a clear flight path, but with scattered trees or fence posts nearby for adult bluebirds to use as perching spots while hunting. When orienting the house, face the entrance hole toward the east or southeast. This direction helps the nest receive warming morning sun while avoiding the most intense heat of the afternoon and the strongest prevailing winds.
Securing the House and Deterring Predators
To ensure the safety of the nest, the bluebird house must be mounted on a freestanding pole rather than directly onto a tree or wooden fence post. Trees and wooden posts provide easy climbing access for predators like raccoons, opossums, and snakes. The most effective mounting solution involves using a smooth, round metal pole, such as electrical conduit or a sturdy metal T-post.
A predator baffle is a non-negotiable component of a secure bluebird house setup. The most recommended types are the stovepipe baffle or a large, conical baffle, which must be installed on the pole below the nesting box. The baffle should be at least six inches in diameter and twenty-four inches long, installed so it wobbles freely when disturbed, preventing climbing animals from gaining purchase.
To manage competition, particularly from the non-native house sparrow, bluebird boxes should be placed away from farm buildings or dense residential areas where sparrows congregate. If competition is severe, some bluebird enthusiasts use monofilament fishing line strung near the entrance hole, which can deter the house sparrow without affecting the bluebirds.