BirdAnalyst
Species · South Dakota · BBS 2025 Release · 1966–2024

Western Grebe Population Trend in South Dakota

All statesWetland birds

Western Grebe in South Dakota has fallen sharply: down 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 →
14Routes 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 →
34YearsYears 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 South DakotaNotable 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 fallen sharply in South Dakota: down 67% on the route-weighted index since 1988.

Western Grebe Population Forecast in South Dakota

If the recent trend holds, Western Grebe in South Dakota is projected to fall about 56% by 2028 — from 0.40 in 2023 to a central estimate of 0.18 (95% range 0.00–1.1). A 5-year backtest shows a typical error of ±57.6%, with 100% of held-out values landing inside the 95% band.

-56%Change by 2028TrendPercent 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 →
0.18Projected 2028 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–1.195% 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 →
±57.6%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 South Dakota is projected to fall about 56% by 2028 — from 0.40 in 2023 to a central estimate of 0.18 (95% range 0.00–1.1). A 5-year backtest shows a typical error of ±57.6%, with 100% of held-out values landing inside the 95% band.19862028
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 →
20240.200.001.1
20250.200.001.1
20260.190.001.1
20270.180.001.1
20280.180.001.1

Western Grebe Survey Routes in South Dakota

Routes recording Western Grebe in South Dakota.
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 →
Raymond2020142011
Britton1220231999
Long Lake820191986
White Lake620002000
Cottonwood620221995
S. Pioneer420212006
Howard320122012
Roswell219901988
Cedar Pass120021988
Volga120211987
Lacreek120212021
Wilmot120081987
Owanka120142014
Harding120132001

Western Grebe Population Trend in Other States

arizonacaliforniacoloradoidahokansasminnesotamontananebraskanevadanew-mexiconorth-dakotaoregonutahwashingtonwyoming

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