Before chimneys existed, Chimney Swifts relied on old hollow trees for nesting and roosting. They can’t perch, they can only cling to a rough vertical surface. As developers cleared old growth forests, Chimney Swifts began using human-built structures. But building styles have changed, making traditional brick chimneys rarer. Pesticides have reduced the populations of swifts’ insect prey. People can help swifts by leaving brick or stone chimneys open from April to October and avoiding pesticides.

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