BirdAnalyst
Species · BCR 32 · BBS 2025 Release · 1966–2024

Western Grebe In Coastal California

All regionsCoastal CaliforniaWetland birds

Western Grebe in Coastal California has risen sharply: up 67% on the route-weighted index since 1988.

+67%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 →
19Routes 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 →
37YearsYears 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 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 →

Western Grebe has risen sharply in Coastal California: up 67% on the route-weighted index since 1988.

Western Grebe In Coastal California Population Forecast

If the recent trend holds, Western Grebe in Coastal California is projected to fall about 56% by 2029 — from 1.0 in 2024 to a central estimate of 0.44 (95% range 0.00–1.2). A 5-year backtest shows a typical error of ±233%, with 100% of held-out values landing inside the 95% band.

-56%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 →
0.44Projected 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 →
0.00–1.295% 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 →
±233%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 Coastal California is projected to fall about 56% by 2029 — from 1.0 in 2024 to a central estimate of 0.44 (95% range 0.00–1.2). A 5-year backtest shows a typical error of ±233%, 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 →
20250.430.001.2
20260.430.001.2
20270.440.001.2
20280.440.001.2
20290.440.001.2

Routes In Coastal California

Routes recording Western Grebe in Coastal 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 →
Bartlett SpsCALIFORNIA292018
CoyoteCALIFORNIA202024
San YsidroCALIFORNIA161990
HughsonCALIFORNIA132024
CoalingaCALIFORNIA82001
Harbor Lake 2CALIFORNIA52024
South LakeCALIFORNIA52006
Glen Ellen 3CALIFORNIA52024
OrovilleCALIFORNIA32024
Morro BayCALIFORNIA21992
FolsomCALIFORNIA22009
AdelaidaCALIFORNIA21993
Elizabeth LkCALIFORNIA22016
RumseyCALIFORNIA12006
Foster ParkCALIFORNIA11994
FairfaxCALIFORNIA12005
Lake BerryessaCALIFORNIA12024
ZamoraCALIFORNIA12019
CopperopolisCALIFORNIA12022

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