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BirdNote: Early Bird Gets the Nesting Site

Air Date: Week of

Tree Swallow nestbox. (Photo: Mike Hamilton)

Competition for nesting sites is fierce as migrating birds return north for the summer months, but as BirdNote’s Michael Stein reports, clever bluebirds and the tree swallows beat the rush—staking their claim before others have a chance.



CURWOOD: The days are getting longer, and that brings thoughts of spring and its many pleasures. And principal among those are returning birds, as Michael Stein explains in today’s BirdNote.

Nest Cavities – Book Early

[Rapid series of male Tree Swallow’s song-like notes]

A flash of glittering dark blue cuts through the gray of late February, as a male Tree Swallow glides low over a cattail marsh. The Tree Swallow’s liquid notes hint at spring’s approach.

[Repeat rapid series of male Tree Swallow’s song-like notes]

Where a broad, green pasture meets the forest edge, there is a second, even brighter flash of blue. A male bluebird alights on a fence post, the intense blue of its back glints in the welcome sunlight of late winter.

[A bit of Eastern Bluebird song]

Western Bluebird male protects his nesting site from competitors like the starlings and house sparrows. (Photo: Tom Grey©)

Tree Swallows and all three North American bluebird species are among the earliest northbound migrants to arrive, heralding spring a month before the equinox. Both species will nest only in cavities, such as old woodpecker holes or man-made nest-boxes. The supply of such specialized nest sites is limited. Competition is intense. By arriving so early, Tree Swallows and bluebirds improve their chances of finding unoccupied cavities – and they may fiercely guard a nest site until April, before actually nesting.

Both species benefit greatly from nest-box programs. But it is crucial to put up only nest-boxes with very specific hole-sizes that encourage these flashy blue migrants but deter non-native starlings and House Sparrows.

I’m Michael Stein.

Written by Bob Sundstrom
Song of the birds provided by The Macaulay Library of Natural Sounds at the Cornell Lab of Ornithology, Ithaca, New York. Tree Swallow recorded by G.F. Budney. Eastern Bluebird recorded by W.L. Hershberger.
Producer: John Kessler
Executive Producer: Chris Peterson
© 2016 Tune In to Nature.org - for Living on Earth


CURWOOD: You’ll find pictures at our website, LOE.org.



Learn more about early competition for nesting sites on BirdNote

Tips for building and maintaining birdhouses

How to make a birdhouse for just about any bird

More on the Tree Swallow

Audubon’s field guide to the Mountain Bluebird

More about the Mountain Bluebird from Cornell’s Lab of Ornithology

Audubon’s field guide to the Eastern Bluebird

More about the Eastern Bluebird from Cornell’s Lab of Ornithology

Audubon’s field guide to the Western Bluebird

More about the Western Bluebird from Cornell’s Lab of Ornithology


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