Most homeowners were unaware that birds were nesting inside their chimneys until the young swifts started their loud food-begging calls at two weeks of age. It takes about 30 days after hatching for the young to leave the nest. Swifts are highly beneficial birds, do not spread vermin, and only use the chimney during the warm months when the fireplace is dormant. Like other birds protected by the Migratory Bird Treaty Act of 1916, chimney swifts are protected from being pursued, captured or killed.