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

Vesper Sparrow Population Trend in California

All statesGrassland birds

Vesper Sparrow in California has surged: up 638% on the route-weighted index since 1972.

+638%Since 1972TrendPercent 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 →
41Routes 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 →
54YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Vesper Sparrow 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 increasecomputed 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 →

Vesper Sparrow has surged in California: up 638% on the route-weighted index since 1972.

Vesper Sparrow Population Forecast in California

If the recent trend holds, Vesper Sparrow in California is projected to rise about 35% by 2029 — from 0.84 in 2024 to a central estimate of 1.1 (95% range 0.28–2.0). A 5-year backtest shows a typical error of ±119.7%, with 60% of held-out values landing inside the 95% band.

+35%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 →
1.1Projected 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 →
0.28–2.095% 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 →
±119.7%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, Vesper Sparrow in California is projected to rise about 35% by 2029 — from 0.84 in 2024 to a central estimate of 1.1 (95% range 0.28–2.0). A 5-year backtest shows a typical error of ±119.7%, with 60% of held-out values landing inside the 95% band.19702029
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 →
20251.10.272.0
20261.10.272.0
20271.10.272.0
20281.10.282.0
20291.10.282.0

Vesper Sparrow Survey Routes in California

Routes recording Vesper Sparrow 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 →
Macdoel2320191973
Clear Lk Res2020181972
Ravendale1920241978
Goumaz1820111997
Bridgeport1719731973
Last Chance1720191993
Crowder Flat1520192002
Sattley1520241972
Crowley Lake1220241973
Bodie1220241982
Coalinga1019861986
Madeline920241997
Little Truckee920231997
Davis Creek820241972
Tionesta620211997
Tres Pinos519731973
Hackamore420102000
Mt Shasta420051972
Honey Lake220231976
Dorris220181974
Orleans219721972
Crestview220241999
Big Bear219861971
Ingalls220001973
Lakeshore220062006

Vesper Sparrow Population Trend in Other States

arizonacoloradoconnecticutdelawareidahoillinoisindianaiowakansaskentuckymainemarylandmassachusettsmichiganminnesotamissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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