By Chris Williams on August 14, 2017.

When a customer calls to complain of bats nesting in their chimney, we’re always skeptical. Chimneys are not good roosting sites for bats, but they are almost the only roosting sites for a unique bird, the chimney swift. Depending on the time of year, chimney swifts could be nesting in the chimney or just spending the night on their migration route.

Chimney swifts are swallow-like birds that spend almost all of their time on the wing, capturing flying insects like flies and mosquitoes. In that regard, they are similar to bats. They are also mistaken for bats when large numbers are seen circling around chimneys or roofs at dusk. The difference is that bats would be leaving their attic roosts at dusk to feed while swifts would be entering chimneys to spend the night.


These birds are not able to perch, they cling vertically to surfaces, much like woodpeckers. Swifts evolved from nesting in hollow trees to nesting in the old brick chimneys of a hundred years ago that didn’t have metal liners or caps. Chimney swifts were much more common when tall chimneys on apartment buildings and industrial buildings were an everyday sight. The swifts build half cup-shaped nests plastered to the inside surface of chimneys or boiler smoke stacks.

Another interesting fact about chimney swifts is that they are hosts to the chimney swift bug, a blood-sucking parasite that only an expert can tell from a common bed bug. Chimney swift bugs rarely bite people but they can cause quite a panic if they show up in large numbers inside a building after chimney swifts have moved on.

Chimney swifts are protected by federal law and cannot be killed or harassed during nesting season without a federal permit. That means if chimney swifts are nesting in a chimney, the nest cannot be removed and the chimney cannot be screened or capped until the birds leave the area in August or September for South America. During their spring and fall migrations, large numbers of chimney swifts can descend with considerable ceremony to spend the night together in a suitable chimney found along the way.


A homeowner faces a similar situation when bats are roosting in an attic or other void space. Bats, too, are protected by federal law and cannot be removed or blocked from roosting sites during nesting season when young bats may be left behind (See August is the Beginning of Bat Removal Season).

State laws restrict when pest control companies can perform bat exclusion. In our region, beginning in August, we are able to seal up bat entrances in homes after making sure that all bats have left the roosting site. We can only do this bat work for a couple of months to avoid sealing in any bats that may return to spend the winter in attic spaces.

Both chimney swifts and bats are beneficial in eliminating lots of flying insects but it’s not healthy to live with their droppings and parasites in your home (see What’s So Bad About Having Bats in My Attic?). If you have resident bats, now is the time to call Colonial Pest and ask us about our bat exclusion procedures. No bats are harmed during the process.

Photo Credit : By Pearson Scott Foresman – Archives of Pearson Scott Foresman, donated to the Wikimedia Foundation, Public Domain, Link



We’re not satisfied until you are. Learn More