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Barn swallow colony sites are frequently destroyed when old buildings are demolished or sold to new owners, who wish to close them up. Attracting swallows to buildings where they will be allowed to nest has been simply a matter of opening a door or window, perhaps, providing nesting ledges, and leaving the rest to luck. The chances of attracting barn swallows to a specific building are about as good as attracting bats to a bat box. When a building housing a colony of swallows is to be closed, it should be done after the nesting season. Even then, chances are only fair that the colony will establish itself at a safe site the following spring. Homeowners and farmers go to great length to birdproof their garages and other outbuildings to keep out house sparrows. As old barns fall down, fewer and fewer prime swallow sites remain each year, although bridges offer adequate shelter to many colonies. One potential way to establish a new colony in a building is to transport a nest with young from a doomed site. By moving the nest very slowly, the parents will follow and continue to care for the young. When the old site is lost, it would be hoped that the parents, and perhaps, the entire colony would then nest in the new building the following year. The opportunity to test this theory arose in the summer of 1992, when the H.H.S. mail room was closed off to better control humidity.
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