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

American Bittern Population Trend in Washington

All statesWetland birds

American Bittern in Washington has fallen sharply: down 64% on the route-weighted index since 1976.

-64%Since 1976TrendPercent 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 →
17Routes 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 →
44YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable American Bittern Trends in WashingtonNotable 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 →

American Bittern has fallen sharply in Washington: down 64% on the route-weighted index since 1976.

American Bittern Population Forecast in Washington

If the recent trend holds, American Bittern in Washington is projected to stay roughly flat through 2029, near 0.02 (95% range 0.00–0.10). A 5-year backtest shows a typical error of ±31.4%, with 100% of held-out values landing inside the 95% band.

n/aChange 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 →
0.02Projected 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 →
0.00–0.1095% 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 →
±31.4%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, American Bittern in Washington is projected to stay roughly flat through 2029, near 0.02 (95% range 0.00–0.10). A 5-year backtest shows a typical error of ±31.4%, with 100% of held-out values landing inside the 95% band.19742029
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 →
20250.030.000.10
20260.030.000.10
20270.020.000.10
20280.020.000.10
20290.020.000.10

American Bittern Survey Routes in Washington

Routes recording American Bittern in Washington.
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 →
Mendota 2320001990
Turnbull Nwr320162000
Issaquah219861980
South Elma220051984
Moses Lake220041976
Potholes220192013
Everett119981998
Ilwaco119901975
Taholah119891989
Kamilche119881974
Mendota119881977
Mukilteo119981998
Carnation120181990
Columbia Nwr120212005
Mendota 3120242017
Keystone120181996
Raymond119941994

American Bittern Population Trend in Other States

alaskacaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaslouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-dakotaohiooklahomaoregonpennsylvaniasouth-carolinasouth-dakotatexasutahvermontvirginiawest-virginiawisconsinwyoming

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