If you don’t have a chimney, you may not have noticed our acrobatic avian visitors, the chimney swift. These birds, often described as a cigar with wings, spend most of their lives in motion, eating and drinking on the wing. Individuals can fly up to 500 miles each day while catching and consuming insects in flight. These active birds winter in the upper Amazon basin (in Brazil, Peru, Ecuador, and Chile) but return to the eastern half of North America in the spring to nest. Virginia tends to see its first chimney swifts in April or May and nesting occurs between June and August, with each mating pair producing only one brood each year in the wild.
As its name implies, the chimney swift tends to build a nest inside chimneys and similar structures, though prior to the colonization, America chimney swifts often nested in hollow trees. Nests are built of woven twigs and connected to textured vertical surfaces (such as wood, masonry tiles, brick) with the glue-like saliva of the adults. Unlike most birds, chimney swifts cannot perch well on branches and instead prefer textured vertical surfaces. To accommodate this behavior, chimney swifts may have a modified foot shape, though there is some debate on this. At the very least, the fourth toe (usually pointing in reverse for perching birds) moves closer to forward facing in chimney swifts.
Photo credit: Wildlife Rehabilitation Center of Minnesota (https://wrcmn.org/)
This unique perching and nesting behavior brings chimney swifts closer to humans than other birds and, for those with open fireplaces and chimneys, make them more common to find in the home. Nests are generally very securely attached, but if the chimney is dirty then the saliva may weaken, allowing the nest to fall from the chimney wall into the fireplace below. It is also possible for a nestling or juvenile to fall from the nest or lose its hold on the side of the chimney, and end up in the fireplace. If you notice a fallen nest, nestlings, or fledglngs, it is very important to replace the nest or fledglings in the chimney for the parents to finish raising, and so that the young swifts can migrate in the fall with other swifts.
The best place to re-nest or place a fledgling in on the smoke shelf above the damper. Nestlings can be placed in a basket, fledglings directly on the shelf. This helpful diagram shows three different means for replacing the nest correctly. It is important to close the flue and fill any gaps between the flue and the chimney walls with towels so that the birds cannot fall back into the fireplace.
Overall, the chimney swift population has seen a worrying decline in recent years, though the exact cause is contested. The decline in insect populations has likely caused a drop in the population of many aerial insectivores, including the chimney swift. There is also a potential role for habitat loss, with the capping of older chimneys, the lack of chimneys on many new homes, and the reduction in old growth forest. Homeowners may often seek to have the birds removed because of the noise the juveniles make. However, the noise is short lived as juveniles tend to be ready to take flight within a month of hatching. and adults tend to be fairly quiet.
Written by Andrew McCoy
