BirdAnalyst
Species · Colorado · BBS 2026 Release · 1966–2025

Gadwall Population Trend in Colorado

All statesWaterfowl

Gadwall in Colorado has surged: up 99% on the route-weighted index since 1970.

+99%Since 1970TrendPercent 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 →
66Routes 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 →
52YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Gadwall 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 →

Gadwall has surged in Colorado: up 99% on the route-weighted index since 1970.

Gadwall Population Forecast in Colorado

If the recent trend holds, Gadwall in Colorado is projected to rise about 113% by 2030 — from 0.54 in 2025 to a central estimate of 1.1 (95% range 0.57–1.7). A 5-year backtest shows a typical error of ±40.9%, with 80% of held-out values landing inside the 95% band.

+113%Change by 2030TrendPercent 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 →
1.1Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.57–1.795% 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 →
±40.9%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, Gadwall in Colorado is projected to rise about 113% by 2030 — from 0.54 in 2025 to a central estimate of 1.1 (95% range 0.57–1.7). A 5-year backtest shows a typical error of ±40.9%, with 80% of held-out values landing inside the 95% band.19682030
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 →
20261.10.511.7
20271.10.531.7
20281.10.541.7
20291.10.561.7
20301.10.571.7

Gadwall Survey Routes in Colorado

Routes recording Gadwall 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 Rs4820241992
Cochetopa Pass2620251998
Last Chance919741974
Dinosaur920251995
Stillwater Pass820072000
Blackhead Pk819961996
Neegrande720181995
Lay620251997
Wildhorse L520232015
Fort Morgan520111998
Weston Pass520001995
Powderhorn520192019
Guffey420251992
Nunn420182001
Julesburg420042002
Basin420102010
Stoneham420212003
Haswell420221997
Cortez420071990
Falfa319971997
Hudson320211988
Willow Peak320101997
Tarryall320231990
Doyleville320251988
Alamosa320251988

Gadwall Population Trend in Other States

alaskaarizonacaliforniadelawareidahoillinoisindianaiowakansasmassachusettsmichiganminnesotamissourimontananebraskanevadanew-jerseynew-mexiconew-yorknorth-dakotaoklahomaoregonpennsylvaniarhode-islandsouth-dakotatexasutahvermontwashingtonwisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.