BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Chimney Swift

ApodidaeAerial insectivoresChaetura pelagica

Chimney Swift has collapsed: down 75% on the route-weighted index since 1968.

-75%Since 1968TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
2,620RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
58Years SurveyedYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

About the Chimney Swift

A cigar-shaped aerial bird that spends almost its whole life airborne, the Chimney Swift roosts and nests in chimneys and has declined sharply as masonry chimneys disappear.

Size
4.5–6 in long, about 0.8 oz (12–15 cm, 23 g)
Habitat
Open airspace over fields, water and towns; nests in cavities, earthen banks or on structures.
Diet
Flying insects caught on the wing.
Range
Recorded on 2,620 Breeding Bird Survey routes across 40 states, most concentrated in the Appalachian Mountains.
Family
Apodidae · Aerial insectivores
Conservation
Vulnerable

Notable Chimney Swift TrendsNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

long arc declinecomputed indexTrend sourceWhether the figure is our own computed route-weighted index or an official USGS modeled estimate. The current build labels every trend as computed.Full methodology →

Chimney Swift has collapsed in surveyed states: down 75% on the route-weighted index since 1968.

Chimney Swift Population Forecast

If the recent trend holds, Chimney Swift is projected to fall about 35% by 2029 — from 2.2 in 2024 to a central estimate of 1.5 (95% range 0.00–2.9). A 5-year backtest shows a typical error of ±15.1%, with 100% of held-out values landing inside the 95% band.

-35%Change by 2029TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
1.5Projected 2029 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–2.995% range95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
±15.1%Backtest errorBacktest errorTypical error when we hold out the most recent years, forecast them, and compare to what actually happened. Lower means a more trustworthy projection.Full methodology →
If the recent trend holds, Chimney Swift is projected to fall about 35% by 2029 — from 2.2 in 2024 to a central estimate of 1.5 (95% range 0.00–2.9). A 5-year backtest shows a typical error of ±15.1%, with 100% of held-out values landing inside the 95% band.19662029
Projection of the recent trend (dashed) with 80/95% bands — a projection, not a prediction. Habitat, climate, and land use are not modeled.
YearProjected indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →95% low95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →95% high95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
20251.90.413.4
20261.80.303.3
20271.70.183.2
20281.60.073.1
20291.50.002.9

Where the Chimney Swift Is Detected

BBS routes recording Chimney Swift, sized by most recent count.

Chimney Swift Population Trend by State

Chimney Swift population trend by state.
TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Alabama-70%1968109
Arkansas-74%196959
Colorado-82%19708
Connecticut+34%196820
Delaware-41%196817
Florida-29%1968104
Georgia-71%1968109
Illinois-66%1968105
Indiana-48%196869
Iowa-88%196939
Kansas-89%196962
Kentucky-82%196863
Louisiana-11%196999
Maine-56%196873
Maryland-35%196876
Massachusetts-56%196832
Michigan-22%196893
Minnesota-71%196975
Mississippi-77%196870
Missouri-88%196991
Montana-11%19903
Nebraska-57%196955
New Hampshire-62%196825
New Jersey-6%196841
New York-34%1968124
North Carolina-59%1968111
North Dakota-46%196915
Ohio-68%196889
Oklahoma-89%196967
Pennsylvania-36%1968133
Rhode Island+144%19696
South Carolina-77%196851
South Dakota+48%197013
Tennessee-74%196855
Texas-83%1969184
Vermont-77%196826
Virginia-61%196887
West Virginia-71%196862
Wisconsin-55%196896
Wyominginsufficient datan/a4

Chimney Swift Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Chimney Swift population trend by Bird Conservation Region.
TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Prairie Potholes-71%196970
Boreal Hardwood Transition-79%1968102
Lower Great Lakes / St. Lawrence Plain-45%196883
Atlantic Northern Forest-60%1968150
Shortgrass Prairie-50%196933
Central Mixed Grass Prairie-80%1969116
Edwards Plateau-74%197019
Oaks and Prairies-87%196974
Eastern Tallgrass Prairie-77%1968273
Prairie Hardwood Transition-47%1968157
Central Hardwoods-83%1968162
West Gulf Coastal Plain / Ouachitas-71%1969108
Mississippi Alluvial Valley-35%196868
Southeastern Coastal Plain-63%1968342
Appalachian Mountains-54%1968396
Piedmont-58%1968171
New England / Mid-Atlantic Coast-40%1968161
Peninsular Florida-32%196860
Tamaulipan Brushlands-40%197024
Gulf Coastal Prairie-44%196944

Chimney Swift Conservation Status

Vulnerable

The IUCN Red List rates this species as Vulnerable. Our route-weighted index shows it down about 75% since 1968. Aerial insectivores have fallen sharply across the continent, a decline widely linked to dwindling insect prey.

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.