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

Lesser Scaup Population Trend in Colorado

All statesWaterfowl

Lesser Scaup in Colorado has surged: up 568% on the route-weighted index since 1989.

+568%Since 1989TrendPercent 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 →
18Routes 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 →
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 Lesser Scaup Trends in ColoradoNotable 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 →

Lesser Scaup has surged in Colorado: up 568% on the route-weighted index since 1989.

Lesser Scaup Population Forecast in Colorado

If the recent trend holds, Lesser Scaup in Colorado is projected to fall about 29% by 2029 — from 0.83 in 2024 to a central estimate of 0.60 (95% range 0.17–1.0). A 5-year backtest shows a typical error of ±37%, with 80% of held-out values landing inside the 95% band.

-29%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 →
0.60Projected 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 →
0.17–1.095% 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 →
±37%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, Lesser Scaup in Colorado is projected to fall about 29% by 2029 — from 0.83 in 2024 to a central estimate of 0.60 (95% range 0.17–1.0). A 5-year backtest shows a typical error of ±37%, with 80% of held-out values landing inside the 95% band.19802029
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 →
20250.570.150.99
20260.580.151.0
20270.580.161.0
20280.590.171.0
20290.600.171.0

Lesser Scaup Survey Routes in Colorado

Routes recording Lesser Scaup in Colorado.
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 →
Rio Grnds Rs7820241991
Mcphee Res.1220122005
Dinosaur1020121995
Nunn520192019
Tincup320241994
Willow Peak320181988
Walden220161990
Dunckley Pas220172006
Colona220142014
Piedra220232023
Yellowjacket Pass120222011
Lost Lake120022002
Stillwater Pass119991999
Tarryall119891989
Kiowa119801980
Doyleville120121989
Ragged Mtn.120062006
Groundhog Rs119951994

Lesser Scaup Population Trend in Other States

alaskacaliforniaidahoiowakansasmichiganminnesotamontananebraskanevadanew-mexiconorth-dakotaoregonsouth-dakotautahwashingtonwisconsinwyoming

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