Mountain Bluebird and Tree Swallow Nest Boxes in the Bighorn Mountain Region
Bighorn Audubon is the caretaker of 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? Here’s a quick guide to get you started:
Box Design: See http://www.nabluebirdsociety.org/PDF/Mountain.pdf for plans for a bluebird box, which swallows will also readily use. Many other designs will work as well but he floor area should be between 20 and 30 square inches, and the entrance hole should sit at least 6 inches above the floor. The entrance hole can be 1 3/4 to 2 inches in diameter. However, at lower elevations a slightly smaller entrance hole of 1 9/16 inches will prevent box use by European Starlings (starlings are absent at higher elevations). Boxes at low elevations should be well-ventilated. For more helpful information, check out this site: https://nestwatch.org/learn/all-about-birdhouses/features-of-a-good-birdhouse/.
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: http://sialis.org/index.html.
Box monitoring: For information on monitoring as well as a Code of Conduct please see: https://nestwatch.org/learn/how-to-nestwatch/code-of-conduct/.
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 email@example.com.