How to Build Bluebird Houses

MOTHER's children article showcases a young scout who built 100 cardboard homes for bluebirds to help the species survive for his Eagle Scout project.

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Now that the houses were made, how could we get bluebirds to nest in them? I talked to a wildlife extension agent who told me the best time to put up bluebird houses is in late winter or early spring.
ROBERT W. MATTHEWS