Your chances of attracting bluebirds to your nest box are affected by both where you place your nest box and when it is opened for the year.
When
When you put up or open your bluebird box depends on your location. Bluebird boxes should typically be in place by mid-March. If you reside in the southern states where bluebirds are year-round residents, early March is a good time.
In cooler, wetter years, nesting may start later than usual. Don’t worry if you are a little late in getting your house up; not all pairs form up and start nesting early and there is always the opportunity to accommodate the 2nd or 3rd brood for the year.
Patience is a virtue. It may take 2 or 3 years for the bluebirds to first use your nest box. Make sure the box is clean and dry on the inside each spring. If bluebirds or other native nesters do not move in, you may wish to close or take down the nest box for the season to prevent house sparrows from taking up residence.
Where
Bluebird boxes are often pole mounted. Smooth round pipe may be the best choice and is available from almost any hardware store. Wooden poles are also acceptable and widely used. The entrance to the nesting box should be about 5-6 feet above the ground.
Face the box away from prevailing winds. There is some evidence (study done with eastern bluebirds) that boxes facing east have somewhat better success ratios but local conditions are always important.
Ideally, boxes should face toward a tree or shrub which is within 100 feet of the box. This provides easy access for young birds leaving the nest. Some advocate placing a man-made perch 15-20 feet in front of the nest box to provide an easy landing spot for young birds if no natural perch is nearby. (Never place a perch directly on the house itself.)
Bluebirds are most common in rural areas and in the outer edges of suburban developments. Locate your bluebird box in an area relatively free from underbrush, in the open, but near a wooded area. Bluebirds like to perch on a tree limb or telephone wire and observe the open fields, golf courses, meadows or other open ground for the insects on which they feed.
This successful box is located at the edge of a heavily wooded area in a city park. Normally it would be better to locate it in a more open area but this location avoids conflicts with the mowers on their large tractors.
Boxes located near shrubbery and undergrowth tend to be inviting to house wrens and are often more visited by predators.
If raccoons or cats might be present, avoid locating your nest box along a fence line or on a fence post. You may find it necessary to use a baffle or greased pole in any case.
If you establish your own bluebird trail, try to locate your boxes 200 or more yards away from man-made structures such as buildings, bridges and major power poles. This will help limit intrusion by house sparrows, which compete with the bluebirds for nesting locations.