On your most recent visit to the John James Audubon Center at Mill Grove, you may have noticed the tall, white structure pictured above located by the new parking lot to the cottage. Though it may look a little strange, this structure plays an important part for conservation. It's the new chimney swift tower, built as an Eagle Scout project by Mark Frederick and designed to provide a place for chimney swifts to roost and nest.
Chimney swifts are known in the birding community as “flying cigars” that buzz our cities and waterways. They arrive in our area in late April and can be observed flitting through our skies catching insects on the wing. It is presumed that before European settlers, these delightful birds nested and roosted in old hollowed out trees. When the Europeans brought with them the architectural structure of the chimney, chimney swifts found these stone “hollow trees” perfect for nesting and roosting. Over time they became dependent on these chimneys and, in turn, became more urban. Today chimney swifts are in decline due to changes in chimney management. Chimneys are increasingly being capped to prevent “critters” access and chimney swifts are finding fewer sites to meet their needs. That is why the installation of chimney swift towers is so important. By placing these towers in correct locations we are trying offset the decline of chimney swifts by providing new nesting and roosting sites.
Chimney swifts are fascinating birds that spend a great deal of the day on the wing and spend their evenings attached to the interior wall of a chimney or other dark crevice. They are insectivores and capture their prey in mid-air. Chimney swifts winter in South America along the upper Amazon Basin of Brazil, Peru, Columbia, and Ecuador, and arrive in Southeastern Pennsylvania in late April and early May for breeding. Chimney swifts build a half cup structure on the interior wall of the chimney with small sticks that are glued together with sticky saliva. Both parents build the nest where the female lays 4-5 eggs. Incubation is shared by both parents, and starts after the 2nd to last egg is laid. The eggs hatch after about 19 days and the youngsters are born naked and blind. Once the eggs hatch, the parents get busy catching insects to feed the babies. After two weeks the baby birds may move out of the nest and attach to the interior walls of the chimney. After 30 days they are ready to fledge and directly fly out of the chimney. One fascinating aspect of Chimney Swifts is that only one breeding pair may nest in a chimney with numerous other roosting swifts. Some of the non-breeding birds may help feed the breeding pairs’ young. After the young fledge they catch their own insects and can be seen flying with the other adult birds. A trick you can use to tell adults from juveniles in summer is to look for missing feathers at the first or second primary feather on the wing (primaries are the last 10 feathers at the end of the wing; the ones in question are closest to the bird’s body). Adults start their molt after breeding while recently fledged birds are not missing any flight feathers.
The John James Audubon Center at Mill Grove and the Valley Forge Audubon Society would like to thank Mark Frederick for taking on this challenging project. We hope the Chimney Swift Tower will provide a nesting and roosting site for many years to come.