BirdAnalyst
Species · BBS 2026 Release · 1966–2025

Cliff Swallow Population Analysis

HirundinidaeAerial insectivoresPetrochelidon pyrrhonota

Cliff Swallow has surged: up 241% on the route-weighted index since 1968.

+241%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 →
2,983RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
59Years 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 Cliff Swallow

A colonial swallow that builds gourd-shaped mud nests under bridges, culverts and eaves, the Cliff Swallow nests in dense colonies that can number in the thousands.

Size
5–5.5 in long, about 0.7 oz (13–14 cm, 21 g)
Habitat
Open airspace over fields, water and towns; nests in cavities, earthen banks or on structures.
Diet
Flying insects taken on the wing, often in swarms.
Range
Recorded on 2,983 Breeding Bird Survey routes across 48 states, most concentrated in the Eastern Tallgrass Prairie.
Family
Hirundinidae · Aerial insectivores
Conservation
Least Concern

Notable Cliff Swallow 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 increasecomputed 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 →

Cliff Swallow has surged in surveyed states: up 241% on the route-weighted index since 1968.

Cliff Swallow Population Forecast

If the recent trend holds, Cliff Swallow is projected to rise about 20% by 2030 — from 16 in 2025 to a central estimate of 19 (95% range 13–24). A 5-year backtest shows a typical error of ±32.5%, with 100% of held-out values landing inside the 95% band.

+20%Change by 2030TrendPercent 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 →
19Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
13–2495% 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 →
±32.5%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, Cliff Swallow is projected to rise about 20% by 2030 — from 16 in 2025 to a central estimate of 19 (95% range 13–24). A 5-year backtest shows a typical error of ±32.5%, with 100% of held-out values landing inside the 95% band.19662030
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 →
2026181324
2027181324
2028191324
2029191324
2030191324

Where the Cliff Swallow Is Detected

BBS routes recording Cliff Swallow, sized by most recent count.

Cliff Swallow Population Trend by State

Cliff Swallow 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 →
Alabama202×197168
Alaska-92%197858
Arizona-56%197052
Arkansas14×197633
California+2%1970217
Colorado-35%1970142
Connecticut-42%19768
Delawareinsufficient datan/a1
Florida+7%19837
Georgia16×199136
Idaho+42%197059
Illinois170×196997
Indiana66×197547
Iowa25×197037
Kansas+296%196965
Kentucky85×197929
Louisiana39×199463
Maine-95%196861
Maryland+190%196921
Massachusetts-61%196915
Michigan-76%196882
Minnesota+279%196982
Mississippi42×198844
Missouri137×197469
Montana+49%1970104
Nebraska+112%196971
Nevada+508%197037
New Hampshire-95%196822
New Jersey-48%19875
New Mexico+148%197071
New York-90%196892
North Carolina+164%197325
North Dakota+154%196951
Ohio15×197143
Oklahoma+365%196962
Oregon-27%1970105
Pennsylvania-50%196885
South Carolina+195%199010
South Dakota+55%196960
Tennessee61×196838
Texas+56%1969231
Utah+91%197088
Vermont-86%196825
Virginia+171%196923
Washington-29%197096
West Virginia-87%197127
Wisconsin-21%196894
Wyoming-25%1970125

Cliff Swallow Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Cliff Swallow 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 →
BCR 2+420%19958
BCR 4-89%197842
Northern Pacific Rainforest-82%1970100
Great Basin+93%1970219
Northern Rockies+16%1970188
Prairie Potholes+252%1969122
Boreal Hardwood Transition-93%1968101
Lower Great Lakes / St. Lawrence Plain+118%196862
Atlantic Northern Forest-96%1968129
Sierra Nevada+7%197029
Southern Rockies / Colorado Plateau+37%1970192
Badlands and Prairies-42%1969134
Shortgrass Prairie-15%1969118
Central Mixed Grass Prairie+216%1969125
Edwards Plateau-87%197120
Oaks and Prairies+234%196972
Eastern Tallgrass Prairie131×1968223
Prairie Hardwood Transition+138%1968142
Central Hardwoods109×1971111
West Gulf Coastal Plain / Ouachitas35×197672
Mississippi Alluvial Valley162×199552
Southeastern Coastal Plain175×1971106
Appalachian Mountains+757%1968213
Piedmont21×197073
New England / Mid-Atlantic Coast-13%196825
Coastal California+9%1970117
Sonoran and Mojave Deserts-17%197046
Sierra Madre Occidental-61%197123
Chihuahuan Desert+63%196952
Tamaulipan Brushlands-82%196927
Gulf Coastal Prairie40×198037

Cliff Swallow Conservation Status

Least Concern

The IUCN Red List rates this species as Least Concern. Our route-weighted index shows it up about 241% 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 2026-08-14. Trend is a route-weighted relative-abundance index, not an absolute population.