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Bluebird Trail


FAQs About the Refuge Bluebird Trail

Why are there nest boxes along the refuge roadways?
These wooden boxes, about 190 of them over the whole refuge, attract Eastern bluebirds, whose numbers had dropped nationwide in the last century. Bluebirds nest in tree and fence post cavities, but had greatly lost those spots to more aggressive non-native house sparrows. Thanks to thousands of nesting boxes set up on public and private land, bluebirds began a comeback by the 1970s which has resulted in a thriving population today.

What's the history of the Crab Orchard NWR bluebird trail?
In 1989 a zoology professor at Southern Illinois University Carbondale proposed that boxes be established in the refuge. Funding came from the Southern Illinois Audubon Society, which paid for 125 boxes and posts. Initially the boxes were made from tar paper covered milk cartons set into wooden frames.  Volunteer monitors recorded data about the birds' use of the boxes and the trail coordinator wrote an annual report summarizing the results. Today almost all of the boxes are made from cypress, cedar, or pine. From 1989 through 2016, we estimate that at least 25,000 birds have been fledged from the refuge boxes.

Are Eastern bluebirds the only species that use the boxes?
Tree swallows, house wrens, and Carolina chickadees typically choose the refuge boxes, too. For years we've also had an established return of prothonotary warblers (31 fledged in 2016). Like the bluebirds, all of these species are protected by law.

How are the boxes monitored?
The nesting season starts in mid-March when Eastern bluebirds begin pairing up and looking for nest sites. The volunteers check their section of the trail weekly and write down the type of nest, the number of eggs, the number of hatchlings, and the number that have successfully fledged. The weekly monitoring continues until mid-August when the season for most species has ended. Occationally a bluebird will have a successful nesting even into mid-September.

Why does plastic pipe cover the posts that hold the boxes?
Bluebird boxes attract several types of predators who will eat the eggs and often the young birds still on the nest. Most of the poles are covered with two 20" sections of common PVC pipe. This has virtually eliminated predation from raccoons, which had been a big problem in the past. The pipe is too slippery for the raccoon to use to reach the box opening.
 The other common predator -- snakes -- can be discouraged through a metal cone placed around the pole just under the bottom of the box. However, large snakes often succeed in climbing over the cone and into the box. Since the cones are fairly expensive, not every box has one.

Who pays for the costs of the CONWR bluebird trail?
 Friends of Crab Orchard Refuge has been contributing $300 annually. The trail coordinator also has an annual grant through the Southern Illinois Audubon Society. These donations help us buy replacement boxes and boxes to expand the trail into new areas, as well as to purchase a few more predator guards each year. Otherwise, volunteers pay for their own tools and supplies.
 Your membership in Friends of Crab Orchard Refuge is very important and appreciated to continue our many programs that support the refuge and its wildlife.

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