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Species · California · BBS 2025 Release · 1966–2024

Barn Swallow Population Trend in California

All statesAerial insectivores

Barn Swallow in California has surged: up 90% on the route-weighted index since 1970.

+90%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 →
56YearsYears 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 90% 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 37% by 2029 — from 6.2 in 2024 to a central estimate of 3.9 (95% range 0.37–7.5). A 5-year backtest shows a typical error of ±36.4%, with 100% of held-out values landing inside the 95% band.

-37%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 →
3.9Projected 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 →
0.37–7.595% 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 →
±36.4%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 37% by 2029 — from 6.2 in 2024 to a central estimate of 3.9 (95% range 0.37–7.5). A 5-year backtest shows a typical error of ±36.4%, with 100% of held-out values landing inside the 95% band.19682029
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 →
20254.20.617.7
20264.10.557.7
20274.10.497.6
20284.00.437.6
20293.90.377.5

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
Likely9020241971
Ora Loma8220241972
Coalinga6520141986
Dorris4720191972
Crescent Cty3520241972
Collegeville 23420232007
Westley3120241972
Tres Pinos 22820112005
Coyote2620241972
Greenfield2620241973
Moreno2320241981
Blythe2019791974
Zamora2020241972
Staten Is.2020241994
Palo Verde1820231973
Bartlett Sps1820181972
Hollister 21820242012
Niland1420232017
Bodega Bay1420211972
Rio Dell1320121972
Buena Vista1320181990
Pescadero1320241992
Riovista1220241968

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 2026-05-22.