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

Gadwall Population Trend in Idaho

All statesWaterfowl

Gadwall in Idaho has surged: up 162% on the route-weighted index since 1973.

+162%Since 1973TrendPercent 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 →
28Routes 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 →
49YearsYears 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 IdahoNotable 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 Idaho: up 162% on the route-weighted index since 1973.

Gadwall Population Forecast in Idaho

If the recent trend holds, Gadwall in Idaho is projected to rise about 39% by 2029 — from 0.60 in 2024 to a central estimate of 0.83 (95% range 0.18–1.5). A 5-year backtest shows a typical error of ±59.9%, with 100% of held-out values landing inside the 95% band.

+39%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 →
0.83Projected 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 →
0.18–1.595% 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 →
±59.9%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 Idaho is projected to rise about 39% by 2029 — from 0.60 in 2024 to a central estimate of 0.83 (95% range 0.18–1.5). A 5-year backtest shows a typical error of ±59.9%, with 100% of held-out values landing inside the 95% band.19712029
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 →
20250.800.151.5
20260.810.161.5
20270.820.171.5
20280.830.181.5
20290.830.181.5

Gadwall Survey Routes in Idaho

Routes recording Gadwall in Idaho.
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 →
Featherville820012001
Cedar Hill620241998
Cabarton620231986
Naples520241988
Blackft Res420181984
Mud Lake420221988
Blacks Creek319751971
Cascade219841984
Centerville220111973
Springfield220171972
Triangle220241996
Henry219831973
Sawtooth City 2220162016
Iron Springs220241988
Picabo220161988
Daniels Res220041988
Sawtooth Cty219911991
Pasadena Val220081990
Kyle Canyon119971997
Cape Horn119921992
Squirrel119991999
Craters119861984
Magic Mtn120232009
Acequia119791979
Pocatello119921992

Gadwall Population Trend in Other States

alaskaarizonacaliforniacoloradodelawareillinoisiowakansasmassachusettsmichiganminnesotamissourimontananebraskanevadanew-jerseynew-mexiconew-yorknorth-dakotaoklahomaoregonpennsylvaniarhode-islandsouth-dakotatexasutahvermontwashingtonwisconsinwyoming

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