Last updated: 4 January 2023
The Chimney Swift (Chaetura pelagica) is a fascinating and delightful little bird from the Apodidae family. One of just four American species, they are the only Swift that birdwatchers can see in the eastern half of the USA and Canada. Have you ever wondered where and how these Swifts nest?
Chimney Swifts take their name from their habit of nesting in chimneys. In wilderness areas, these hummingbird relatives find nesting opportunities in hollow trees. Both parents assist in building the nest and raising four or five altricial chicks.
Chimney Swifts have benefitted from the development of North America through the increased abundance of nest sites in the last few centuries.
However, the species is in decline at present. Concerned birdwatchers can help the birds in their area by erecting a Chimney Swift nest tower.
This article covers the nesting habits of the Chimney Swift. Read along to learn how these masters of the skies build their unusual nests in North American Homes.
A large nesting colony of Chimney Swifts nesting in a chimney
Chimney Swifts overwinter in the Amazon Basin in South America and return to nest across the eastern half of the USA each spring. One or both Swifts in a pair will scout for the nest site before beginning construction.
Chimney Swifts nest in dark and sheltered sites with vertical walls. They favor chimneys, but they will build their nest in the following locations:
Natural sites
Artificial sites
Chimney Swifts have been nesting in chimneys in North America for hundreds of years. Most pairs now nest in chimneys, although many build their nests elsewhere in buildings or use natural tree cavities and caves.
Chimney Swifts generally use the same roost and nest sites year after year.
Chimney Swifts are more likely to nest in your home or on a built structure on your property than in your backyard. However, these swallow-like birds will use backyards with suitable nest sites like purpose-made nest boxes.
Chimney Swift in flight catching insect
Chimney Swifts readily use nest boxes, although these structures differ from your regular birdhouse. The most effective nest boxes are made from timber with grooves on the inside to give the birds purchase and a place to secure their nest.
These nest boxes are known as towers. They consist of a tall column with ventilation near the top entrance and smooth outer walls to deter predators like snakes and raccoons.
Chimney Swifts still nest in trees in areas where chimneys are not available. However, chimneys and other artificial structures are certainly favored.
A 2014 review found that Chimney Swifts nest and roost in no less than thirteen species of living, dead, or dying coniferous and deciduous trees. Suitable trees are generally large and hollow or have cavities.
Chimney Swifts are known to nest in the following tree species:
Chimney Swift nest heights vary depending on the nature of the nest site structure. In chimneys in Kansas, most nests are built about ten feet (3 m) below the entrance. The average height of 25 roost and nest trees was 42 feet (12.7 m).
Chimney Swift nesting tower
Chimney Swift nests are not easy to spot because they are well hidden. Here’s what they look like.
Chimney Swift nests are saucer-shaped with a flat side where they are attached to the wall or other vertical structure. The front rim of the nest is often lower than the back attachment point, creating a sloping or hanging effect. Chimney Swift nests have a coarse appearance due to the large diameter of the twigs used.
Chimney Swift nests are small, and the chicks typically outgrow them long before they are ready to become independent.
Chimney Swifty nest dimensions:
Chimney Swifts could be called cavity nesters. They build small saucer or shallow cup-shaped nests.
Roosting Chimney Swifts retuning to their nests at night
Chimney Swifts visit the United States and Canada at the same time each year to nest and raise the next generation. Continue reading to learn about the timing of their breeding season.
Chimney Swifts begin nesting in the spring or summer. In Texas, nest construction begins in late April. Further north in Canada, nest construction may conclude in early June.
Chimney Swift nesting usually takes about two and a half months. Building their nests may take up to a month, and the chicks are relatively slow to reach flying age for a bird of their size. Read on for a timeline of Chimney Swift nesting.
Most Chimney Swifts lay their eggs in March or June. The timing varies somewhat according to latitude.
Chimney Swifts are migratory birds that do not nest in the northern winter. They overwinter in countries like Chile, Brazil, and Peru in the western half of South America.
Tower for Chimney Swifts, to nest and roost in a nature preserve in west central Florida
Building a sturdy nest on a vertical wall presents quite a challenge. Continue reading to learn their secret.
Chimney Swifts gather the twigs by snapping them off the tree in flight. They do most of their building in the afternoon and evening. Chimney Swifts develop enlarged saliva glands in the nesting season, and they use this sticky substance to glue the twigs in place while building their nest.
Chimney Swift nests are made from small twigs and glued together with their sticky saliva. They use whatever twigs are readily available in their area.
Both male and female Chimney Swifts work on the nest. Each bird collects their own material before returning to the nest site, positioning it, and securing it with saliva.
Most birdwatchers never get to see Chimney Swift eggs due to their habit of nesting in dark and inaccessible places. Continue reading to learn more about Chimney Swift eggs.
Chimney Swifts lay slightly glossy white eggs that measure just over three-quarters of an inch long and just over half an inch across (20.5 x 13.5mm).
Chimney Swifts usually lay four or five eggs. However, some nests contain as few as two or as many as seven eggs.
Both males and females develop a brood patch. They sit on the eggs for about 19 days, taking turns to incubate for ten to two hundred minutes. Incubating birds wait until they are relieved by their partner.
Baby Swifts hatch out as tiny, pink, and helpless chicks. A single bird broods during the day, and both parents share the nest with the growing chicks at night.
Baby Swifts leave the nest when they are 14 to 19 days old. They are forced to cling to the wall when they outgrow their nest. Naturally, this happens sooner in nests with larger broods.
The young Swifts don’t fly before they are nearly a month old. This means they may spend nearly two weeks outside of the nest.
Chimney Swifts usually produce a single brood each year. However, some pairs have second broods.
Chimney Swifts abandon their nests each year before migrating south for the winter. They rarely reuse their nests, so cleaning and servicing chimneys after the birds have left does not impact them.
Chimney Swifts do not nest on the ground. They have relatively specialized nesting requirements, and true to their name, most pairs nest in chimneys.
Chimney Swifts roost in sheltered cavities like chimneys and hollow trees. Pairs roost together at the nest site during the breeding season, and both parents will sleep in the nest until the space becomes too limited. They roost communally at other times of the year.
You can attract nesting Chimney Swifts by leaving your chimney uncovered or erecting a Chimney Swift nest tower.
The Migratory Bird Treaty Act protects nesting Chimney Swifts. It is an offense to interfere with their nests during the breeding season. However, you may remove the nests once the chicks have fledged.
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