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

Western Grebe Population Trend in Montana

All statesWetland birds

Western Grebe in Montana has surged: up 89% on the route-weighted index since 1991.

+89%Since 1991TrendPercent 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 →
11Routes 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 →
25YearsYears 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 MontanaNotable 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 surged in Montana: up 89% on the route-weighted index since 1991.

Western Grebe Population Forecast in Montana

If the recent trend holds, Western Grebe in Montana is projected to stay roughly flat through 2029, near 0.12 (95% range 0.00–0.34). A 5-year backtest shows a typical error of ±297.1%, with 100% of held-out values landing inside the 95% band.

n/aChange 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 →
0.12Projected 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 →
0.00–0.3495% 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 →
±297.1%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 Montana is projected to stay roughly flat through 2029, near 0.12 (95% range 0.00–0.34). A 5-year backtest shows a typical error of ±297.1%, 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 →
20250.120.000.34
20260.120.000.34
20270.120.000.34
20280.120.000.34
20290.120.000.34

Western Grebe Survey Routes in Montana

Routes recording Western Grebe in Montana.
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 →
Hebgen Lake420232017
Beaverhead220181986
Red Rock219941988
Shawmut220232018
Lindsay120192019
Libby Dam119861986
Kalispell120031991
Great Falls120151994
Highwood120082008
Jordan120172017
Two Dot120241988

Western Grebe Population Trend in Other States

arizonacaliforniacoloradoidahokansasminnesotanebraskanevadanew-mexiconorth-dakotaoregonsouth-dakotautahwashingtonwyoming

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