BirdAnalyst
Species · BCR 15 · BBS 2025 Release · 1966–2024

Vaux's Swift In Sierra Nevada

All regionsSierra NevadaAerial insectivores

Vaux's Swift in Sierra Nevada has fallen sharply: down 65% on the route-weighted index since 1975.

-65%Since 1975TrendPercent 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 →
14Routes 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 →
36YearsYears 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 →

Vaux's Swift has fallen sharply in Sierra Nevada: down 65% on the route-weighted index since 1975.

Forecast

If the recent trend holds, Vaux's Swift in Sierra Nevada is projected to fall about 41% by 2029 — from 0.21 in 2024 to a central estimate of 0.13 (95% range 0.00–0.36). A 5-year backtest shows a typical error of ±232.8%, with 100% of held-out values landing inside the 95% band.

-41%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 →
0.13Projected 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 →
0.00–0.3695% 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 →
±232.8%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 Sierra Nevada is projected to fall about 41% by 2029 — from 0.21 in 2024 to a central estimate of 0.13 (95% range 0.00–0.36). A 5-year backtest shows a typical error of ±232.8%, with 100% of held-out values landing inside the 95% band.19732029
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 →
20250.140.000.37
20260.130.000.37
20270.130.000.37
20280.130.000.37
20290.130.000.36

Routes In Sierra Nevada

Routes recording Vaux's Swift in Sierra Nevada.
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 →
StrawberryCALIFORNIA61999
LakeshoreCALIFORNIA52003
Butte MeadowCALIFORNIA41997
Hat CreekCALIFORNIA32002
Bass LakeCALIFORNIA22011
Tuolumne GroveCALIFORNIA22024
WawonaCALIFORNIA22024
CrestviewCALIFORNIA22000
Eagle LakeCALIFORNIA11974
DardanelleCALIFORNIA11986
JohnsvilleCALIFORNIA12013
GeneseeCALIFORNIA12018
RivertonCALIFORNIA11989
Pollock PinesCALIFORNIA11999

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