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

Western Grebe In Sierra Nevada

All regionsSierra NevadaWetland birds

Western Grebe in Sierra Nevada has held roughly steady: up 7% on the route-weighted index since 1988.

+7%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 →
4Routes 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 →
35YearsYears 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 →

No notable trend signals for Western Grebe in Sierra Nevada. See the full index history below.

Western Grebe In Sierra Nevada Population Forecast

If the recent trend holds, Western Grebe in Sierra Nevada is projected to fall about 27% by 2029 — from 0.68 in 2024 to a central estimate of 0.50 (95% range 0.00–2.4). A 5-year backtest shows a typical error of ±31.3%, with 100% of held-out values landing inside the 95% band.

-27%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 →
0.50Projected 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 →
0.00–2.495% 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 →
±31.3%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 Sierra Nevada is projected to fall about 27% by 2029 — from 0.68 in 2024 to a central estimate of 0.50 (95% range 0.00–2.4). A 5-year backtest shows a typical error of ±31.3%, 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 →
20250.540.002.4
20260.530.002.4
20270.520.002.4
20280.510.002.4
20290.500.002.4

Routes In Sierra Nevada

Routes recording Western Grebe 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 →
Eagle LakeCALIFORNIA132024
ChilcootCALIFORNIA31998
SattleyCALIFORNIA22019
GeneseeCALIFORNIA12019

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