BirdAnalyst
Species · California · BBS 2025 Release · 1966–2024

White-throated Swift Population Trend in California

All statesAerial insectivores

White-throated Swift in California has fallen sharply: down 57% on the route-weighted index since 1970.

-57%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 →
136Routes 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 →
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 White-throated 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 →

White-throated Swift has fallen sharply in California: down 57% on the route-weighted index since 1970.

White-throated Swift Population Forecast in California

If the recent trend holds, White-throated Swift in California is projected to fall about 38% by 2029 — from 1.2 in 2024 to a central estimate of 0.71 (95% range 0.00–2.2). A 5-year backtest shows a typical error of ±39.9%, with 100% of held-out values landing inside the 95% band.

-38%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 →
0.71Projected 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 →
0.00–2.295% 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 →
±39.9%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 California is projected to fall about 38% by 2029 — from 1.2 in 2024 to a central estimate of 0.71 (95% range 0.00–2.2). A 5-year backtest shows a typical error of ±39.9%, 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 →
20250.810.002.3
20260.780.002.3
20270.760.002.3
20280.730.002.3
20290.710.002.2

White-throated Swift Survey Routes in California

Routes recording White-throated 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 →
Kings Canyon3120241972
Angelus Oaks2620171989
Santa Ynez2020191981
Kernville2020082008
Parker Dam1620071975
El Toro1519991995
Coyote1520241972
Copperopolis1320241972
Silver City1120131973
Joshua Tree 21120142014
San Ysidro1020191986
Lake Success1019801972
Fallsvale919811970
Elizabeth Lk920151970
Riovista820192004
Green Valley820221974
Westley820192004
Sawmill Mtn720221970
Lake Hemet719741971
Creston720241972
San Benito Mtn.720092003
Wawona720241998
Lake Cachuma620161974
Hat Creek620002000
Harbor Lake 2620242014

White-throated Swift Population Trend in Other States

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