BirdAnalyst
Species · California · BBS 2026 Release · 1966–2025

Barn Swallow Population Trend in California

All statesAerial insectivores

Barn Swallow in California has surged: up 116% on the route-weighted index since 1970.

+116%Since 1970TrendPercent 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 →
193Routes In StateSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
57YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Barn Swallow Trends in CaliforniaNotable 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 →

Barn Swallow has surged in California: up 116% on the route-weighted index since 1970.

Barn Swallow Population Forecast in California

If the recent trend holds, Barn Swallow in California is projected to fall about 38% by 2030 — from 6.5 in 2025 to a central estimate of 4.1 (95% range 0.48–7.6). A 5-year backtest shows a typical error of ±40.5%, with 100% of held-out values landing inside the 95% band.

-38%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 →
4.1Projected 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 →
0.48–7.695% 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 →
±40.5%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, Barn Swallow in California is projected to fall about 38% by 2030 — from 6.5 in 2025 to a central estimate of 4.1 (95% range 0.48–7.6). A 5-year backtest shows a typical error of ±40.5%, with 100% of held-out values landing inside the 95% band.19682030
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 →
20264.30.707.9
20274.20.647.8
20284.20.597.8
20294.10.537.7
20304.10.487.6

Barn Swallow Survey Routes in California

Routes recording Barn Swallow in California.
Recent countThe raw number of individuals recorded on this route in its most recent survey year. A single-route tally, not a trend.Full methodology →
Orland20120221972
Tranquillity10720241973
Ora Loma8120251972
Likely7120251971
Coalinga6520141986
Niland5520252017
Dorris4720191972
Crescent Cty3620251972
Westley3520251972
Collegeville 23420232007
Coyote3320251972
Glenn3220251971
Tres Pinos 22820112005
Riovista2120251968
Moreno2020251981
Blythe2019791974
S Catalina1920251988
Bartlett Sps1820181972
Hollister 21820242012
Ingalls1520251973
Bodega Bay1420211972
Rio Dell1320121972
Greenfield1320251973
Korbel1320251972
Buena Vista1320181990

Barn Swallow Population Trend in Other States

alabamaalaskaarizonaarkansascoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.