BirdAnalyst
Species · BCR 32 · BBS 2025 Release · 1966–2024

Barn Swallow In Coastal California

All regionsCoastal CaliforniaAerial insectivores

Barn Swallow in Coastal California has surged: up 206% on the route-weighted index since 1970.

+206%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 →
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 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 206% 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 27% by 2029 — from 9.1 in 2024 to a central estimate of 6.6 (95% range 3.2–10). A 5-year backtest shows a typical error of ±38%, with 80% of held-out values landing inside the 95% band.

-27%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 →
6.6Projected 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 →
3.2–1095% 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 →
±38%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 27% by 2029 — from 9.1 in 2024 to a central estimate of 6.6 (95% range 3.2–10). A 5-year backtest shows a typical error of ±38%, with 80% 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 →
20256.63.210.0
20266.63.210.0
20276.63.210.0
20286.63.210
20296.63.210

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 LomaCALIFORNIA822024
CoalingaCALIFORNIA652014
Collegeville 2CALIFORNIA342023
WestleyCALIFORNIA312024
Tres Pinos 2CALIFORNIA282011
CoyoteCALIFORNIA262024
GreenfieldCALIFORNIA262024
MorenoCALIFORNIA232024
ZamoraCALIFORNIA202024
Staten Is.CALIFORNIA202024
Bartlett SpsCALIFORNIA182018
Hollister 2CALIFORNIA182024
Buena VistaCALIFORNIA132018
PescaderoCALIFORNIA132024
RiovistaCALIFORNIA122024
OilfieldsCALIFORNIA122013
AuburnCALIFORNIA121980
HollisterCALIFORNIA112011
Elizabeth LkCALIFORNIA112016
HughsonCALIFORNIA102023
S CatalinaCALIFORNIA102022
PenningtonCALIFORNIA92024
Tres PinosCALIFORNIA82003

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.