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Species · California · BBS 2025 Release · 1966–2024

Western Grebe Population Trend in California

All statesWetland birds

Western Grebe in California has collapsed: down 80% on the route-weighted index since 1988.

-80%Since 1988TrendPercent 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 →
38Routes 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 →
38YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Western Grebe 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 →

Western Grebe has collapsed in California: down 80% on the route-weighted index since 1988.

Western Grebe Population Forecast in California

If the recent trend holds, Western Grebe in California is projected to rise about 206% by 2029 — from 0.66 in 2024 to a central estimate of 2.0 (95% range 0.00–7.2). A 5-year backtest shows a typical error of ±3863.2%, with 100% of held-out values landing inside the 95% band.

+206%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 →
2.0Projected 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 →
0.00–7.295% 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 →
±3863.2%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, Western Grebe in California is projected to rise about 206% by 2029 — from 0.66 in 2024 to a central estimate of 2.0 (95% range 0.00–7.2). A 5-year backtest shows a typical error of ±3863.2%, with 100% of held-out values landing inside the 95% band.19862029
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 →
20252.10.007.3
20262.10.007.3
20272.10.007.2
20282.00.007.2
20292.00.007.2

Western Grebe Survey Routes in California

Routes recording Western Grebe 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 →
Iron Gate12420191988
Dorris5620191986
Bartlett Sps2920181986
Coyote2020242000
San Ysidro1619901990
Eagle Lake1320241986
Hughson1320241987
Navarro1019901990
Coalinga820011998
South Lake520062006
Harbor Lake 2520242018
Glen Ellen 3520242024
Fish Rock320101988
Madeline320171999
Oroville320241993
Chilcoot319981998
Elizabeth Lk220162016
Sattley220191989
Macdoel219981989
Clear Lk Res220181986
Laytonville219891988
Morro Bay219921992
Folsom220091992
Adelaida219931993
Nubieber120171986

Western Grebe Population Trend in Other States

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