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Bighorn Audubon, with the help of a great team of volunteers, maintains and monitors hundreds of Mountain Bluebird and Tree Swallow nest boxes in the Bighorn National Forest.

Many of these boxes have been in place for decades and have brought much joy to residents and visitors. Thousands of young have been fledged from these boxes over the years helping to maintain healthy populations of the two species. With the help of dedicated volunteers our goal is to provide, maintain, and monitor the nest boxes to ensure continued success of these species in our area.


Interested in nest boxes of your own?

If you would like to build boxes, it is important to choose the right materials, make sure the box is not too small or large, and has the right-sized entrance hole.  Do not use treated wood because of the chemicals that wood contains.  Wood used should be at least 3/4 inches thick.  Thinner wood, such as plywood, does not provide adequate insulation from either the cold of the mountains or the intense solar radiation in the foothills.  Boxes positioned below about 6000 ft elevation in the foothills should have adequate ventilation for hot summer days.


The box should have a floor area of at least 20 square inches but no more than about 50 square inches.  The box should be tall enough such that the bottom of the entrance hole is at least 5 inches but no more than about 8 inches from the floor.  


The ideal diameter for the entrance hole is 1 9/16 inches.  This is just large enough to permit entry by a bluebird but quite not large enough for the invasive European Starling.  If you don’t have a 1 9/16 inch bit, you can drill a 1 ½ inch hole and use a round or rattail file to enlarge it slightly.   

Click here for further useful information:

Plans for a new box can also be found here:


Box placement: While Tree Swallows occur at most elevations, Mountain Bluebirds usually only breed at elevations above 5,000 feet. Both Mountain Bluebirds and Tree Swallows prefer to nest well out in grassy areas away from shrubs and trees (boxes near shrubs and trees often attract House Wrens). Swallows will sometimes take boxes away from bluebirds so where both species occur it is good to erect two boxes 15-30 feet apart so swallows have their own home.


Boxes should sit at least 5 feet above ground and be located in areas where livestock cannot rub or chew on them. For maximum enjoyment, you want to be able to see the entrance and watch the birds come and go. All else being equal, though, the entrance should open to the southeast, away from the prevailing winds and driving rain and snow.


While nest predators are rare in the mountains, nests below ~6000 ft can be pilfered by a variety of species including cats, raccoons, snakes, weasels, squirrels, chipmunks, and even mice. Boxes at lower elevations should be mounted on smooth metal poles (such as 3/4 inch electrical conduit) coated with thick grease or, better yet, a predator guard positioned immediately below the box. Inexpensive, easy-to-attach cone or flying saucer-shaped metal guards are available online. Other types of guards you can make are described at this very helpful site:


Box monitoring: For information on monitoring as well as a Code of Conduct please see:


Box maintenance: In fall, clean out your boxes. Neither bluebirds nor swallows remove old nesting material and build new nests on top of old nests, eventually making the box too shallow for birds to use. When removing a nest from a box, be sure to avoid inhaling the dust that is released; it is best to wear a mask and gloves. Deposit the nest at least 30 feet from the box so as to not attract predators. Come early spring, check and repair any damage from the winter. Bluebirds begin arriving in March and nest building may take place as early as mid-April. Swallows return in mid to late April.


For more information please contact JoAnne Puckett with Bighorn Audubon at

Mt Bluebird (2).JPG
Bluebirds in the Bighorns
Tree Swallow photo courtesy of Bighorn Audubon JP
Tree Swallow
bluebird usfs 1.JPG
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