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

Gadwall Population Trend in California

All statesWaterfowl

Gadwall in California has surged: up 11× on the route-weighted index since 1973.

11×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 →
57Routes 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 →
53YearsYears 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 CaliforniaNotable 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 California: up 11× on the route-weighted index since 1973.

Gadwall Population Forecast in California

If the recent trend holds, Gadwall in California is projected to rise about 145% by 2029 — from 1.6 in 2024 to a central estimate of 4.0 (95% range 0.57–7.5). A 5-year backtest shows a typical error of ±1026.7%, with 20% of held-out values landing inside the 95% band.

+145%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 →
4.0Projected 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 →
0.57–7.595% 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 →
±1026.7%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 California is projected to rise about 145% by 2029 — from 1.6 in 2024 to a central estimate of 4.0 (95% range 0.57–7.5). A 5-year backtest shows a typical error of ±1026.7%, with 20% 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 →
20253.80.377.3
20263.90.427.3
20273.90.477.4
20284.00.527.4
20294.00.577.5

Gadwall Survey Routes in California

Routes recording Gadwall in California.
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 →
Dorris21220191972
Likely7320241975
Benton3820242004
Madeline2220241998
Jacumba2019881988
Poloma1520132008
Macdoel1420191980
Cedarville1420191974
Iron Gate1320191994
Big Bear1119861974
Mesa Grande619981998
Crowley Lake520241974
Cp. Pendleton519911989
Glenn420071987
Lockwood420242024
Ora Loma420241973
Tres Pinos320022001
Crowder Flat320182013
Davis Creek320241975
Ingalls320011973
Buena Vista320171993
Nubieber220181971
Pennington220091984
Hughson220241985
Westley220181999

Gadwall Population Trend in Other States

alaskaarizonacoloradodelawareidahoillinoisiowakansasmassachusettsmichiganminnesotamissourimontananebraskanevadanew-jerseynew-mexiconew-yorknorth-dakotaoklahomaoregonpennsylvaniarhode-islandsouth-dakotatexasutahvermontwashingtonwisconsinwyoming

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