BirdAnalyst
Species · California · BBS 2026 Release · 1966–2025

Vaux's Swift Population Trend in California

All statesAerial insectivores

Vaux's Swift in California has fallen sharply: down 66% on the route-weighted index since 1971.

-66%Since 1971TrendPercent 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 →
61Routes 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 →
55YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Vaux's Swift 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 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 →

Vaux's Swift has fallen sharply in California: down 66% on the route-weighted index since 1971.

Vaux's Swift Population Forecast in California

If the recent trend holds, Vaux's Swift in California is projected to stay roughly flat through 2030, near 0.18 (95% range 0.00–0.36). A 5-year backtest shows a typical error of ±303.4%, with 40% of held-out values landing inside the 95% band.

n/aChange 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 →
0.18Projected 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 →
0.00–0.3695% 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 →
±303.4%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, Vaux's Swift in California is projected to stay roughly flat through 2030, near 0.18 (95% range 0.00–0.36). A 5-year backtest shows a typical error of ±303.4%, with 40% 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 →
20260.180.000.37
20270.180.000.37
20280.180.000.37
20290.180.000.37
20300.180.000.36

Vaux's Swift Survey Routes in California

Routes recording Vaux's Swift 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 →
Redwood N.P. 22220132012
Anza Borrego1219901990
Martins Fy720081976
Adelaida719771977
Orange Cove620021994
Strawberry619991999
Coyote520222012
Lakeshore520032003
Red Bluff420111994
Iron Gate420191989
Dorris420152011
Butte Meadow419971973
Lake Success419781977
Copperopolis420172017
Horse Creek320171972
Nubieber319971997
Hat Creek320021973
Rio Dell320061974
Crescent Cty220241972
Redwood N.P.220071995
Bass Lake220112006
Tuolumne Grove220242006
Fall River Mills220111998
Longvale220171998
Orleans220041983

Vaux's Swift Population Trend in Other States

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