Chirping in the Chimney
If you have been hearing a fast, high-pitched chirping sound in your chimney, it probably belongs to the Chimney Swift—a small, slender, dark-grey bird with an erratic flight pattern that often causes them to be mistaken for bats. They spend most of their time in flight, landing only to sleep at night or to feed their young during nesting season. Since they are unable to perch like other birds, they will often nest in chimneys and other vertical spaces. They live primarily in the eastern half of United States from around late March through early November during breeding season.
Swifts are a migratory bird and are protected under the Migratory Bird Treaty Act, which states that birds and nests cannot be removed without a Federal permit. A certified chimney sweep can remove the birds upon inspection, whether you want to keep them away or are happy to host your little winged guests.
First, if you have a metal flue, it is very important to cap your chimney. Metal flues are dangerous, since birds and animals are unable to grip the metal and can fall to their death or become trapped inside the chimney. A chimney cover will keep rain, debris and animals out of your chimney.
Chimney swifts can only nest in masonry chimneys lined with clay or stone. They build their nests by attaching small twigs to the inside of the chimney with saliva. These birds aren’t noisy until the young begin to chirp for meals, which lasts only a couple of weeks. Since swifts eat 1/3 of their weight in insects (mosquitoes included), they can help keep you bug-free and might be worth the noise. Have your chimney cleaned in early March to clear creosote buildup and then again in late fall to remove nesting debris if you want to give these bird a safe place to nest.
If you have a masonry chimney and want to keep swifts out, wait until late fall when the birds have migrated, then have your chimney cleaned and install a cover.