BirdAnalyst
Species · BCR 32 · BBS 2026 Release · 1966–2025

Barn Swallow In Coastal California

All regionsCoastal CaliforniaAerial insectivores

Barn Swallow in Coastal California has surged: up 219% on the route-weighted index since 1970.

+219%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 →
94Routes In RegionSurvey 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 SignalsNotable 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 Coastal California: up 219% on the route-weighted index since 1970.

Barn Swallow In Coastal California Population Forecast

If the recent trend holds, Barn Swallow in Coastal California is projected to fall about 20% by 2030 — from 8.4 in 2025 to a central estimate of 6.8 (95% range 3.4–10). A 5-year backtest shows a typical error of ±39.7%, with 80% 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 →
6.8Projected 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 →
3.4–1095% 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 →
±39.7%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 Coastal California is projected to fall about 20% by 2030 — from 8.4 in 2025 to a central estimate of 6.8 (95% range 3.4–10). A 5-year backtest shows a typical error of ±39.7%, with 80% 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 →
20266.73.310
20276.73.410
20286.83.410
20296.83.410
20306.83.410

Routes In Coastal California

Routes recording Barn Swallow in Coastal 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 →
OrlandCALIFORNIA2012022
TranquillityCALIFORNIA1072024
Ora LomaCALIFORNIA812025
CoalingaCALIFORNIA652014
WestleyCALIFORNIA352025
Collegeville 2CALIFORNIA342023
CoyoteCALIFORNIA332025
GlennCALIFORNIA322025
Tres Pinos 2CALIFORNIA282011
RiovistaCALIFORNIA212025
MorenoCALIFORNIA202025
S CatalinaCALIFORNIA192025
Bartlett SpsCALIFORNIA182018
Hollister 2CALIFORNIA182024
GreenfieldCALIFORNIA132025
Buena VistaCALIFORNIA132018
OilfieldsCALIFORNIA122013
AuburnCALIFORNIA121980
PescaderoCALIFORNIA122025
HollisterCALIFORNIA112011
Elizabeth LkCALIFORNIA112016
Mark WestCALIFORNIA92025
Staten Is.CALIFORNIA92025
Tres PinosCALIFORNIA82003
ReddingCALIFORNIA81983

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