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

Northern Rough-winged Swallow In Coastal California

All regionsCoastal CaliforniaAerial insectivores

Northern Rough-winged Swallow in Coastal California has fallen sharply: down 65% on the route-weighted index since 1970.

-65%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 →
105Routes 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 declinecomputed 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 →

Northern Rough-winged Swallow has fallen sharply in Coastal California: down 65% on the route-weighted index since 1970.

Northern Rough-winged Swallow In Coastal California Population Forecast

If the recent trend holds, Northern Rough-winged Swallow in Coastal California is projected to fall about 20% by 2029 — from 1.0 in 2024 to a central estimate of 0.84 (95% range 0.00–2.7). A 5-year backtest shows a typical error of ±47.5%, with 100% of held-out values landing inside the 95% band.

-20%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 →
0.84Projected 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 →
0.00–2.795% 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 →
±47.5%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, Northern Rough-winged Swallow in Coastal California is projected to fall about 20% by 2029 — from 1.0 in 2024 to a central estimate of 0.84 (95% range 0.00–2.7). A 5-year backtest shows a typical error of ±47.5%, 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 →
20250.950.002.8
20260.920.002.8
20270.890.002.8
20280.870.002.8
20290.840.002.7

Routes In Coastal California

Routes recording Northern Rough-winged 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 →
OilfieldsCALIFORNIA772005
OrlandCALIFORNIA401992
CollegevilleCALIFORNIA322002
El ToroCALIFORNIA231999
BakersfieldCALIFORNIA172023
Orange CoveCALIFORNIA152012
Elizabeth LkCALIFORNIA142016
SisquocCALIFORNIA132014
AthloneCALIFORNIA112007
Jofegan 2CALIFORNIA112024
CrestonCALIFORNIA92023
Carrizo PlnCALIFORNIA92021
Cp. PendletonCALIFORNIA82004
PowayCALIFORNIA71980
AdelaidaCALIFORNIA71999
MoragaCALIFORNIA62023
CoyoteCALIFORNIA62024
Anza 2CALIFORNIA62005
Staten Is.CALIFORNIA62024
Foster ParkCALIFORNIA51994
Morro BayCALIFORNIA51991
VentucopaCALIFORNIA52002
GreenfieldCALIFORNIA52024
Glen EllenCALIFORNIA52002
AlamarCALIFORNIA52009

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