BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Western Grebe

PodicipedidaeWetland birdsAechmophorus occidentalis

Western Grebe has fallen sharply: down 71% on the route-weighted index since 1988.

-71%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 →
221RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
38Years SurveyedYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

About the Western Grebe

The Western Grebe (Aechmophorus occidentalis) is a North American member of the Grebes (Podicipedidae). In this analysis it is grouped with the wetland birds.

Size
9–21.5 in long (23–55 cm) — a diving water bird (typical for the family)
Habitat
Marshes, ponds, lakeshores and other freshwater wetlands.
Diet
Aquatic invertebrates, small fish, frogs and plant matter.
Range
Recorded on 221 Breeding Bird Survey routes across 16 states, most concentrated in the Great Basin.
Family
Podicipedidae · Wetland birds

Notable Western Grebe TrendsNotable 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 surveyed states: down 71% on the route-weighted index since 1988.

Western Grebe Population Forecast

If the recent trend holds, Western Grebe is projected to rise about 142% by 2029 — from 0.07 in 2024 to a central estimate of 0.17 (95% range 0.00–0.44). A 5-year backtest shows a typical error of ±156.1%, with 100% of held-out values landing inside the 95% band.

+142%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 →
0.17Projected 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 →
0.00–0.4495% 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 →
±156.1%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 is projected to rise about 142% by 2029 — from 0.07 in 2024 to a central estimate of 0.17 (95% range 0.00–0.44). A 5-year backtest shows a typical error of ±156.1%, 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 →
20250.190.000.46
20260.180.000.46
20270.180.000.45
20280.180.000.45
20290.170.000.44

Where the Western Grebe Is Detected

BBS routes recording Western Grebe, sized by most recent count.

Western Grebe Population Trend by State

Western Grebe population trend by state.
TrendPercent 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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Arizona-11%19994
California-80%198838
Colorado+3%199221
Idaho-91%198815
Kansasinsufficient datan/a1
Minnesotainsufficient datan/a5
Montana+89%199111
Nebraska-17%19945
Nevada-93%19947
New Mexico-24%20004
North Dakota+149%198822
Oregon-94%198817
South Dakota-67%198814
Utah+230%199223
Washington-61%19907
Wyoming+43%198927

Western Grebe Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Western Grebe population trend by Bird Conservation Region.
TrendPercent 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 →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Northern Pacific Rainforest-92%19897
Great Basin-92%198853
Northern Rockies-82%198839
Prairie Potholes-15%198831
Sierra Nevada+7%19884
Southern Rockies / Colorado Plateau+202%199029
Badlands and Prairies+55%199118
Shortgrass Prairie-37%19967
Central Mixed Grass Prairie+6%19946
Coastal California+67%198819
Sonoran and Mojave Deserts+99%19975

Western Grebe Conservation Status

Our route-weighted index shows it down about 71% since 1988.

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.