Chimney Swifts

As their name implies, they build their nests in chimneys as well as abandoned buildings and stone wells. Chimney Swifts are usually single-brooded meaning that there will be only one active nest in any structure regardless of the size of the site. Swifts arrive in the continental United States in late March and are gone by early November. Nesting begins in May, and sometimes continues into August. Every chimney should be professionally cleaned each year for the safety of the homeowner as well as for the safety of the Chimney Swifts. They are protected by State Wildlife Codes and Federal law under the Migratory Bird Treaty Act of 1916; there is up to a $15,000 fine per bird and egg and possible jail penalty for removing active nests.

The female normally lays three to five white eggs in a nest of twigs which are broken from the tips of tree branches, glued together with saliva and attached to a vertical surface. Both sexes are involved in nest construction. The eggs are incubated by alternating adults for eighteen to nineteen days. Both parents feed the babies, eats flying insects including mosquitoes and termites. The feeding continues until about 30 days after hatching. Twenty-eight to thirty days after hatching, young Chimney Swifts will leave the safety of the chimney for their first flight. Once an entire brood has fledged*, they will fly with their parents in slow, noisy parades around the area of the nest site. They congregate in flocks of hundreds and even thousands at suitable roost sites. Chimney swifts can nest more than once in a season. Although Chimney Swifts can withstand a few early cool snaps, they will usually fly south with the first major cold-front in the fall.

While chimney swifts don’t spread disease in and of themselves, their droppings can be a source of histoplasmosis**, a respiratory infection caused by the fungus. This is generally a problem when droppings have been allowed to accumulate over a long period of time.

Once the sound of the young becomes noticeable, they are usually only 10 days or so from fledgling*. Keeping the damper closed and packing the fireplace with insulation can dampen the sound to tolerable levels.


  • Chimney Swifts eat nearly one third of their own weight in flying insect pests such as mosquitoes, biting flies and termites every day.
  • Today, just like Purple Martins, Chimney Swifts rely almost entirely on man-made structures for nest sites.
  • Because they cannot perch like songbirds, Chimney Swifts must have deep shafts (like chimneys) in which to raise their families and roost at night.
  • Like watching a beautiful sunset, the aesthetic value of observing Chimney Swifts’ aerial acrobatics and interactions is a simple pleasure that nature has to offer.


  • If you have a masonry or clay flue-tile chimney, keep the top open and the damper closed from March through October to provide a nest site for these insect-eaters.
  • If you have a metal chimney, it should be permanently capped to prevent birds and other wildlife from being trapped.
  • Have your chimney cleaned in early March before the Chimney Swifts return from their winter home in South America.

*Fledgling (birds): a young bird that has recently left its nest but is still dependent upon parental care and feeding

**Histoplasmosis is often a mild, self-limiting disease that basically healthy people may ignore or perhaps not even notice. However histoplasmosis can be very dangerous or even life threatening for those who are very young, very old, or suffering from a compromised immune system.