The Eastern Bluebird (Sialia sialis) is a small North American thrush, recognizable by the male’s brilliant blue back and head, contrasting with a reddish-brown breast and white belly. This species ranges across eastern North America, from southeastern Canada down to the Gulf states. Although its population is currently stable, the species faced a significant decline in the mid-20th century due to habitat loss and competition from non-native birds. Its successful recovery is largely attributed to the widespread installation of specialized nest boxes and supplemental feeding. Attracting these birds requires a strategic approach that addresses their distinct needs for protein-rich food, clean water, and predator-protected nesting sites.
Supplying Specialized Food and Water
Eastern Bluebirds are primarily insectivores, with invertebrates making up approximately 68% of their diet, especially during the breeding season when they are feeding their young. Unlike many common backyard birds, bluebirds rarely eat seed, making specialized offerings necessary for successful attraction. The most effective supplemental food is the mealworm, which can be offered live or freeze-dried.
Mealworms should be placed in a dedicated feeder designed to deter larger, aggressive birds like European Starlings. Effective designs include specialized bluebird feeders with small entrance holes, often 1.5 inches in diameter, or barrier-guarded feeders that utilize a wire cage to restrict access. Live mealworms are preferred, but freeze-dried versions are easier to store and can be offered in a smooth-sided dish or glass bowl to prevent them from crawling out.
In addition to insects, bluebirds will consume berries and suet, particularly in the fall and winter when insects are scarce. Offer suet nuggets or cakes that are insect-based or contain berries, avoiding traditional seed or peanut suet blends. Providing a consistent source of fresh water is equally important for attracting bluebirds and other insect-eating species.
A shallow bird bath, no more than three inches deep, with a rough surface for secure footing, is ideal. Bluebirds are highly attracted to the sound and sight of moving water, which often signifies freshness. Adding a water dripper, mister, or a water wiggler to the bath will create ripples and droplets, acting as a powerful visual and auditory attractant. Ensure the bird bath is cleaned frequently and placed in an open area, about 15 feet away from dense shrubs where predators may hide.
Choosing and Placing Nest Boxes
Because Eastern Bluebirds are secondary cavity nesters, relying on pre-existing holes for shelter, providing appropriate housing is the most direct way to establish a presence. The nest box should be constructed from untreated, weather-resistant wood, such as cedar or redwood, with boards at least three-quarters of an inch thick for insulation. Proper design requires a hinged side panel for cleaning, small drainage holes in the floor, and ventilation gaps near the roofline to manage interior temperature.
The entrance hole diameter must measure 1.5 inches to allow access for the bluebird while excluding the larger European Starling. The interior floor should be a minimum of 4 by 4 inches, and the box should never include a perch, which only assists competing birds and predators. Positioning the box correctly is as important as its construction.
Mount the nest box on a smooth, metal pole or electrical conduit, not on a tree or wooden fence post, which climbing predators can easily scale. The entrance hole should sit five to seven feet above the ground for optimal safety. A cone or stovepipe baffle must be installed on the pole below the box to deter climbing mammals like raccoons and snakes from reaching the nest.
The box should be placed in an open area, such as a field edge or large lawn, facing an open space rather than dense woods. Orienting the entrance hole toward the east or north helps avoid direct, intense afternoon sun and prevailing winds, which can lead to overheating or rain entering the box. If placing multiple boxes, they should be spaced at least 100 yards apart, as bluebirds are territorial during the breeding season.
Maintaining a Safe Backyard Environment
Creating a suitable foraging landscape is necessary to support the bluebirds that the feeders and nest boxes attract. Bluebirds primarily hunt by perching on an elevated spot and swooping down to the ground to catch insects, a foraging technique called drop-hawking. This behavior dictates their preference for open, short-grass areas like lawns, meadows, or pastures, where they can easily spot prey.
The presence of scattered perches, such as low tree branches, fence posts, or utility wires, provides the vantage points for hunting. Landowners should avoid the use of chemical pesticides and herbicides, which directly eliminate the insects and spiders that form the majority of the bluebird diet. The decline of the insect population makes the area unsuitable for bluebirds, even with supplemental feeding.
Aggressive competitors for nesting sites, particularly the House Sparrow and European Starling, must be closely monitored. Since these two species are not protected by federal law, their nests, eggs, or young can be legally removed from a bluebird box immediately upon discovery. Regular monitoring allows for prompt removal of competitor nesting material, which encourages bluebirds to settle and successfully raise their broods.