Mountain bluebird secrets revealed

By Stephen Clearheart Johnson
North Forty News

Mountain bluebirds love to nest in secondhand cavities such as an abandoned woodpecker hole, but they can't make their own holes. Humans, too, can help by building nesting boxes as bluebirds come under increased habitat pressure.

Bluebirds will reward a nest-box builder by returning each year for up to 10 years, producing 10 to 15 progeny each year and providing many colorful displays and courtship calls.

These were some of the tips and secrets revealed to a Red Feather Lakes audience by Kevin Corwin, coordinator of the Colorado Bluebird Project. His mission is to improve bluebird vitality by educating the public and teaching construction, care and monitoring of nesting boxes. His project provides nesting kits for $20 per box.

Because the beloved mountain bluebird is larger than both the western and eastern varieties (all of which can be found in Colorado), nesting boxes should have an entry hole of exactly 1 9/16 inches. The roof should slope to shed water and have an overhang sufficient to offset the long reach of a raccoon or housecat.

Boxes should be monitored frequently and occasionally cleaned or repaired. Boxes should be installed on posts, not trees, at a height of 5 feet for easy monitoring and placed near open grassy fields where the mountain bluebird can forage for insects. The hole should face southeast. Monitoring rewards the box-builder with insights into the progress of nest and fledglings. The results can be logged and reported to Cornell University, which conducts ongoing research into bluebird populations.

One secret to building the nest box is that on the inside, below the access hole, a series of parallel grooves like a ladder is needed to allow swallows to escape. Otherwise, the swallows can enter but are unable to fly out. A perch below the hole should not be used as it encourages house sparrows, which attack bluebird eggs.

Mountain bluebirds use grass to build their nests. If twigs are found, wrens are present. If feathers are found, sparrows have invaded. Both these nests should be removed.

Nest activity can be viewed by opening a hinged side panel or using an angled reflective mirror to see through the entry hole. Once eggs are detected, the box should not be opened because the mother may panic and desert the nest. The eggs incubate for two weeks. The fledglings grow fast and will fly two to three weeks after hatching.

The nesting boxes are generally constructed of 1-inch cedar or pine, with a floor 5 inches square and a height of about 1 foot. Ventilation and drainage must be provided. Kits can be purchased from the Colorado Bluebird Project, and do-it-yourselfers can find many available plans through an online search.

Corwin's presentation was co-sponsored by the Mountain Gals social club and the Red Feather Mountain Library District. The Colorado Bluebird Project functions under the Audubon Society of Greater Denver. More information can be found online at www.denveraudubon.org/bluebird.htm.