Thursday, June 18, 2009

Bluebirds, Swallows, and Nest Boxes

Beginning in the 1970s peopled rallied to restore the beautiful Eastern bluebird, which was in a serious population decline. The causes of the decline? Changes in habitat for one. Bluebirds live in open areas--fields, orchards, farmland, beaver ponds, pitch pine-oak forests, clearings made by fire or logging. And they nest in cavities, in holes made by woodpeckers. By the 1970s, abandoned farms were being reclaimed by forest, metal fence posts replaced wooden posts, orchards and other habitats were converted to human settlements. Also, as an insect-eater, the bluebird's food source was likely contaminated by pesticides.

To bring back the bluebird, a campaign began and is still underway to build and maintain bluebird nest boxes. Some people maintain dozens of nest boxes along a "bluebird trail." Detailed information is available at several places -- the North American Bluebird Society and Sialis -- on how to build, place, and monitor bluebird boxes. This has been a hugely successful effort, engaging young and old in observing these beautiful birds.

The Eastern bluebird is a smaller version of a robin, one of its close relatives. The bluebird's cobalt blue head and back contrast with its rusty throat and breast. A somewhat plump bird, it perches and watches the ground, abruptly flying down to capture a grasshopper, cricket, beetle, spider, or caterpillar. Before nest boxes arrived, bluebirds nested in dead or dying trees at the edge of wetlands, in trees killed by fire or beaver, or in apple trees. In addition to nest boxes, it is important to maintain these natural cavities and the surrounding habitats.

Old apple tree, male bluebird seen visiting the holes

The specifications for building and placing nest boxes are precise (see websites above) to ensure maximum success and to deter predators and competitors. One potential competitor is another attractive native bird, the tree swallow, which is also deserving of nest boxes and observation.

photo by Amy Snyder, Charlotte, Vermont

The tree swallow's iridescent blue head and back and snow white throat and breast are striking. Its streamlined body slices through the air above as it captures dragonflies, moths, flies, and other flying insects on the wing.

Bluebirds and tree swallows can nest side-by-side. Try mounting pairs of nest boxes, about 10 feet apart. Individual or pairs of boxes should then be spaced about 300 feet apart to encourage multiple birds to nest.

To avoid another native, but pesky, cavity-nester, the house wren, place nest boxes more than 200 feet from woods or brushy areas. A nest box full of sticks is a sure sign of a house wren, which will first remove any other nest, eggs, and young. This is a bit of a judgement since the wren is also native, but the wren seems to do well in other natural habitats. And I guess looks do matter, since the wren is a little brown bird that can hardly compete with the glamorous bluebird and tree swallow.

A nice tree swallow tree at the edge of Winterberry Pond

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