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

Black-chinned Sparrow Population Trend in California

All statesGeneralists

Black-chinned Sparrow in California has fallen sharply: down 68% on the route-weighted index since 1970.

-68%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 →
59Routes 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 Black-chinned 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 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 →

Black-chinned Sparrow has fallen sharply in California: down 68% on the route-weighted index since 1970.

Black-chinned Sparrow Population Forecast in California

If the recent trend holds, Black-chinned Sparrow in California is projected to fall about 90% by 2029 — from 0.93 in 2024 to a central estimate of 0.09 (95% range 0.00–2.1). A 5-year backtest shows a typical error of ±96.7%, with 100% of held-out values landing inside the 95% band.

-90%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 →
0.09Projected 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 →
0.00–2.195% 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 →
±96.7%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, Black-chinned Sparrow in California is projected to fall about 90% by 2029 — from 0.93 in 2024 to a central estimate of 0.09 (95% range 0.00–2.1). A 5-year backtest shows a typical error of ±96.7%, 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 →
20250.200.002.2
20260.170.002.2
20270.140.002.1
20280.120.002.1
20290.090.002.1

Black-chinned Sparrow Survey Routes in California

Routes recording Black-chinned 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 →
Cuyamaca Pk2620241970
Anza 21620242005
Elsinore Mtn1620241970
Woodlands1520242012
Big Bear1419861969
Lake Hemet 21420231992
Cleveland Nf1420181994
Lake Cachuma1220141980
Green Valley1120231970
Cleveland Nf 2920222019
Oak Grove720241975
Alamar620171997
Lake Hemet519771970
Jacumba420241973
Jofegan420092007
Sawmill Mtn420221970
Fallsvale419811970
Cholla Gard.320012000
San Benito Mtn.320092003
Mt Pinos320041969
Stonyford320162015
Creston219831981
Yokohl Val219781977
Foster Park219811972
Barstow219681968

Black-chinned Sparrow Population Trend in Other States

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