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

Green Heron Population Trend in Washington

All statesWetland birds

Green Heron in Washington has fallen sharply: down 73% on the route-weighted index since 1978.

-73%Since 1978TrendPercent 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 →
21Routes 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 →
35YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Green Heron 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 →

Green Heron has fallen sharply in Washington: down 73% on the route-weighted index since 1978.

Green Heron Population Forecast in Washington

If the recent trend holds, Green Heron in Washington is projected to stay roughly flat through 2023, near 0.02 (95% range 0.00–0.09). A 5-year backtest shows a typical error of ±122.6%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2023TrendPercent 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 2023 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.0995% 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 →
±122.6%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, Green Heron in Washington is projected to stay roughly flat through 2023, near 0.02 (95% range 0.00–0.09). A 5-year backtest shows a typical error of ±122.6%, with 100% of held-out values landing inside the 95% band.19692023
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 →
20190.020.000.10
20200.020.000.10
20210.020.000.10
20220.020.000.09
20230.020.000.09

Green Heron Survey Routes in Washington

Routes recording Green Heron 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 →
Montesand320052004
Mendota 2319951995
Taholah219961987
South Elma220181986
Pe Ell219961994
Yakima219941994
Carnation220101996
Ozette119921992
Kamilche120171978
Issaquah119861969
Mcchord120141997
Bunker Hill119981997
Camas120012001
Kendall120001985
Ilwaco119791978
Mendota119821982
Raymond120071993
Bay View120122004
Mukilteo119971995
Rainier119981998
Mendota 3120182018

Green Heron Population Trend in Other States

alabamaarizonaarkansascaliforniaconnecticutdelawarefloridageorgiaillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourinebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontvirginiawest-virginiawisconsin

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