Chimney swifts live across eastern North America during the breeding season, ranging from southern Canada east of Saskatchewan down through the United States east of Texas. In winter, they migrate to the upper Amazon basin in South America. For most of the year, these small, cigar-shaped birds depend on vertical structures like chimneys and hollow trees for nesting and roosting.
Breeding Range in North America
During spring and summer, chimney swifts occupy a broad swath of the eastern half of the continent. Their range extends north into the Canadian provinces of Ontario and Quebec, and south and west through most states east of the Great Plains. You can find them in cities, suburbs, and rural areas from New England to Florida and from the Atlantic coast to eastern Texas.
Populations are present across the northeastern U.S. (New York, Massachusetts, Connecticut, New Jersey, Pennsylvania, Vermont) and throughout the Southeast and Midwest. However, breeding bird surveys running from 1966 through 2022 show declining numbers in virtually every region tracked, making them a conservation watchlist species in several states.
Wintering Grounds in South America
Once breeding season ends, chimney swifts leave North America entirely. They winter in the upper Amazon basin, spread across parts of Peru, Ecuador, Chile, and Brazil. Relatively little is known about their behavior during these months because the birds are difficult to track in dense tropical forest. At the end of summer, they gather in groups of thousands before making the long flight south.
Migration Timing by Region
Chimney swifts don’t arrive everywhere at once. Their northward push in spring follows a predictable wave tied to latitude and insect availability:
- Southeast and Southwest U.S.: arrive late March, depart mid-October
- Mid-Atlantic: arrive mid-April, depart mid-October
- Northeast and Midwest: arrive late April, depart early October
- Intermountain West: arrive early May, depart mid-September
If you’re trying to spot chimney swifts overhead, those windows tell you when to look. Southern states get nearly seven months with swifts present, while northern and western areas may see them for only four and a half months.
Chimneys, Hollow Trees, and Other Nesting Sites
Before European colonization created millions of brick and stone chimneys across North America, chimney swifts nested inside hollow trees, particularly large old-growth species with wide, dark cavities. As forests were cleared and buildings went up, the birds adapted remarkably well. Today, open masonry chimneys are their primary nesting and roosting habitat, which is how they got their common name.
A nesting pair builds a small half-saucer shaped nest from twigs snapped off the tips of tree branches while the bird is in flight. They glue the twigs together and attach the nest to the inner wall of a chimney using their own sticky saliva. The female typically lays three to five white eggs in this structure. Only one nest occupies a chimney at a time during the breeding season, though the same chimney may host different pairs in successive years.
The shift to man-made structures was a huge advantage for centuries, but it’s now becoming a problem. Modern chimneys are often capped, lined with metal flue liners (which are too smooth for swifts to cling to), or simply absent from newer construction. The loss of suitable chimneys is considered a major driver of the species’ long-term population decline.
Roosting Behavior During Migration
Outside of breeding season, chimney swifts are intensely social. During fall migration especially, hundreds or even thousands of birds will funnel into a single large chimney at dusk to roost overnight. Watching a swirling cloud of swifts spiral down into a chimney is one of the more dramatic wildlife spectacles in urban North America, and it happens in cities and towns across the eastern U.S. every September and October.
These communal roosts tend to use larger structures: old factory smokestacks, school chimneys, or church towers. The birds cling to the interior walls in dense clusters, sharing body heat. Favorite roost sites are used year after year, and local birding groups often track and publicize them during migration season.
How to Tell If Swifts Are in Your Chimney
If you hear a loud, chattering or buzzing sound coming from your fireplace during summer, you likely have nesting chimney swifts. The noise gets louder as chicks grow and beg for food, usually peaking a few weeks before the young fledge. The nesting cycle from egg-laying to fledging takes roughly six weeks.
Chimney swifts are protected under the Migratory Bird Treaty Act, which means it is illegal to remove or disturb active nests, eggs, or birds. If swifts have moved into your chimney, the practical approach is to wait until they leave in fall, then cap or screen the chimney before the following spring. The birds eat enormous quantities of flying insects, including mosquitoes and beetles, so many homeowners consider them welcome guests.