BirdAnalyst
Species · California · BBS 2026 Release · 1966–2025

Great Blue Heron Population Trend in California

All statesWetland birds

Great Blue Heron in California has increased: up 49% on the route-weighted index since 1970.

+49%Since 1970TrendPercent 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 →
158Routes 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 →
57YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Great Blue 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 Great Blue Heron in California. See the full index history below.

Great Blue Heron Population Forecast in California

If the recent trend holds, Great Blue Heron in California is projected to stay roughly flat through 2030, near 0.80 (95% range 0.20–1.4). A 5-year backtest shows a typical error of ±79%, with 80% of held-out values landing inside the 95% band.

+6%Change by 2030TrendPercent 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 →
0.80Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.20–1.495% 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 →
±79%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, Great Blue Heron in California is projected to stay roughly flat through 2030, near 0.80 (95% range 0.20–1.4). A 5-year backtest shows a typical error of ±79%, with 80% of held-out values landing inside the 95% band.19682030
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 →
20260.820.221.4
20270.820.221.4
20280.810.211.4
20290.810.211.4
20300.800.201.4

Great Blue Heron Survey Routes in California

Routes recording Great Blue 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 Gate2420191988
Ora Loma1220251972
Jofegan 21120252025
Hollister1020071975
Shafter719881987
Yreka720191973
Lake Success619811972
Collegeville 2620232007
Horse Creek520191970
Auburn519791970
Coyote520251972
Crescent Cty420221972
Bass Lake420091978
Fairfax420241972
Niland420251974
Westley420251972
Dorris420191972
Clear Lk Res420181972
Staten Is.420251994
Redwood N.P.420101995
Ivanpah320072007
Arvin320211988
Glenn320251971
Atwater320121972
Jackson319861973

Great Blue Heron Population Trend in Other States

alabamaalaskaarizonaarkansascoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.