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

Green Heron Population Trend in California

All statesWetland birds

Green Heron in California has held roughly steady: down 10% on the route-weighted index since 1972.

-10%Since 1972TrendPercent 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 →
93Routes 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 Green Heron 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 →

No notable trend signals for Green Heron in California. See the full index history below.

Green Heron Population Forecast in California

If the recent trend holds, Green Heron in California is projected to stay roughly flat through 2029, near 0.17 (95% range 0.00–0.35). A 5-year backtest shows a typical error of ±399.3%, with 60% 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 →
0.17Projected 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 →
0.00–0.3595% 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 →
±399.3%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 California is projected to stay roughly flat through 2029, near 0.17 (95% range 0.00–0.35). A 5-year backtest shows a typical error of ±399.3%, with 60% of held-out values landing inside the 95% band.19692029
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 →
20250.170.000.35
20260.170.000.35
20270.170.000.35
20280.170.000.35
20290.170.000.35

Green Heron Survey Routes in California

Routes recording Green Heron 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 →
Iron Gate720191988
Cohasset420181977
Poway419801974
Glenn420091973
Ora Loma319741974
Calpella219811971
Foster Park219811981
San Ysidro219921986
Hollister219981978
Orange Cove220111976
Coachella Cn220001987
Ono220101984
Sisquoc219951985
Shafter219881986
Junction Cty220101991
Bodega Bay220061981
Yreka220191979
Glen Ellen220021977
Collegeville 2220092009
Horse Creek120121974
Nubieber120171986
Crescent Cty120031976
Honeydew120122012
Red Bluff120151971
Hullville119861971

Green Heron Population Trend in Other States

alabamaarizonaarkansasconnecticutdelawarefloridageorgiaillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourinebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasvermontvirginiawashingtonwest-virginiawisconsin

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