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

White-throated Swift In Coastal California

All regionsCoastal CaliforniaAerial insectivores

White-throated Swift in Coastal California has fallen sharply: down 71% on the route-weighted index since 1970.

-71%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 →
76Routes 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 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 →

White-throated Swift has fallen sharply in Coastal California: down 71% on the route-weighted index since 1970.

White-throated Swift In Coastal California Population Forecast

If the recent trend holds, White-throated Swift in Coastal California is projected to fall about 47% by 2030 — from 1.0 in 2025 to a central estimate of 0.55 (95% range 0.00–2.5). A 5-year backtest shows a typical error of ±51%, with 100% of held-out values landing inside the 95% band.

-47%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 →
0.55Projected 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 →
0.00–2.595% 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 →
±51%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, White-throated Swift in Coastal California is projected to fall about 47% by 2030 — from 1.0 in 2025 to a central estimate of 0.55 (95% range 0.00–2.5). A 5-year backtest shows a typical error of ±51%, 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 →
20260.640.002.6
20270.620.002.5
20280.590.002.5
20290.570.002.5
20300.550.002.5

Routes In Coastal California

Routes recording White-throated Swift 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 →
Angelus OaksCALIFORNIA262017
CoyoteCALIFORNIA222025
Santa YnezCALIFORNIA202019
El ToroCALIFORNIA151999
CopperopolisCALIFORNIA132024
San YsidroCALIFORNIA102019
Lake SuccessCALIFORNIA101980
FallsvaleCALIFORNIA91981
Elizabeth LkCALIFORNIA92015
Green ValleyCALIFORNIA82022
Sawmill MtnCALIFORNIA72022
Lake HemetCALIFORNIA71974
CrestonCALIFORNIA72024
San Benito Mtn.CALIFORNIA72009
S CatalinaCALIFORNIA62025
Lake CachumaCALIFORNIA62016
Harbor Lake 2CALIFORNIA62024
CoalingaCALIFORNIA52002
PowayCALIFORNIA51980
Mesa GrandeCALIFORNIA52017
Mt Pinos 2CALIFORNIA52024
Tres Pinos 2CALIFORNIA52010
Red BluffCALIFORNIA42024
FairfaxCALIFORNIA42017
Lockwood ValCALIFORNIA42019

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