Bluebirds can readily use help for housing. Bluebirds cannot excavate their own houses. They rely on old woodpecker holes or rotting trees for their homes. A manmade house is a welcome sight to most bluebirds. However, they tend to be a little more picky than most birds about how their house is designed and where it is located.
A good bluebird box should have:
floor size of about 5" x 5"
height should be between 8" to 12"
entrance hole about 6" to 10" above the floor
entrance hole diameter should be 1-1/2"
made of durable wood like cedar,
ventilation holes in the top
drainage holes in the bottom
an easy open front or side to clean out old nests and to check on progress of nesting birds
a few saw kerfs below the hole on inside front of box -- to help the fledglings climb out of the house
no perch -- to discourage access by house sparrows, starlings and blue bird preadators
slightly slanted roof to shed water and keep the contents of the box dry
adaquate drainage in bottom of nesting box
MOUNTING BLUEBIRD BOXES
Bluebird boxes can be mounted on poles, fence posts, utility poles or trees. Posts or poles are the best for providing protection from predators. Purchase commercially available posts from hardware store or use existing fence posts or utility poles. If using a fence post, be sure to mount the box where livestock can't get to it. When possible, face the boxes toward the next fence post so the birds can look into the entrance hole from a perch. Mounting on trees is less desirable because of the threat of climbing predators like cats, raccoons, snakes and squirrels.
The bottom of the nest box should be at least 3 feet above ground. Ideally, it should be mounted 4 to 5 feet above ground. There is no single compass direction that the bluebirds prefer to have the box facing. (I'm not sure of this. I've heard SE is best.) Your main objective should be to deter climbing predators, but allow for easy monitoring. Face the boxes away from prevailing winds. In hot climates, face them to the North or East to avoid direct midday sun. The most important aspect of mounting is to face the box toward some tree or shrub within 100 feet. When the young leave the nest they will make an initial flight to safety.
BEST PLACE TO MOUNT BLUEBIRD BOXES
Make sure you place nest boxes in good bluebird habitat. Not even the best bluebird house will attract bluebirds if it is in the wrong place. Here are some guidelines to follow for good bluebird habitat:
Bluebirds nest primarily in suburban and rural areas.
During breeding, bluebirds hunt insects by scanning the ground from a perch, spotting an insect, then swooping down to the ground to get it. Scattered young trees or shrubs, fence posts and lower branches of a lone mature tree make good hunting perches.
Sparse or low vegetation is also important since it enables the bluebirds to see and capture insects. Cut meadows, mowed lawns and grazed fields are good.
Nest boxes should be at least 100 feet from brushy or wooded areas where wrens are likely to be and preferably at least 1/4 mile from farmyards or barns where sparrows live.
Good areas for bluebird nest boxes include open fields, fence rows, orchards where no pesticides are used, cemeteries, large lawns, golf courses, public parks, along open highways that are kept mowed and pastures.
Mountain bluebirds will nest in open conifer woodlands and in the cliffs or clay banks of river beds.
Proper spacing of nest boxes is important. Bluebirds are territorial when breeding and will claim territories of 2-3 acres. Research shows they will generally not nest closer than 100 yards from the next box.
To keep sparrows out, pair boxes 5-15 feet apart. The sparrows will only nest in one, leaving the other open for the bluebirds.
Providing nesting materials is a strong factor in attracting nesting bluebirds since collecting nesting materials can take hundreds of trips. Bluebirds like soft grasses and fragrant pine needles as nesting material. Provide these nesting materials in a specially designed container, an empty suet cage, or simply gather bunches of material and situate in the bark of a tree.
PROPER MAINTENANCE OF BLUEBIRD HOUSES
Clean bluebird houses after each brood has left. Remove and throw away any old nesting material and scrub with a 10% bleach solution. Old nesting material left on the ground could invite predators. Let dry completely before remounting. This will prevent parasites or diseases from spreading.
WHEN SHOULD BLUEBIRD HOUSES BE INSTALLED?
Anytime and as soon as possible! Bluebirds start looking for breeding nest boxes in February in the South and by mid March in the North. Bluebirds will use them well into August, producing 2-3 broods per year. Consider leaving bluebird boxes up all year. When the mating season is over, birds will use the boxes as winter roosts.