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

Great Blue Heron Population Trend in California

All statesWetland birds

Great Blue Heron in California has edged up: up 19% on the route-weighted index since 1970.

+19%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 →
156Routes 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 →
56YearsYears 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 rise about 22% by 2029 — from 0.67 in 2024 to a central estimate of 0.81 (95% range 0.21–1.4). A 5-year backtest shows a typical error of ±84%, with 80% of held-out values landing inside the 95% band.

+22%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 →
0.81Projected 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 →
0.21–1.495% 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 →
±84%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 rise about 22% by 2029 — from 0.67 in 2024 to a central estimate of 0.81 (95% range 0.21–1.4). A 5-year backtest shows a typical error of ±84%, with 80% of held-out values landing inside the 95% band.19682029
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 →
20250.830.231.4
20260.830.221.4
20270.820.221.4
20280.820.211.4
20290.810.211.4

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
Hollister1020071975
Staten Is.820241994
Hughson720241969
Shafter719881987
Glenn720231971
Ora Loma720241972
Yreka720191973
Lake Success619811972
Collegeville 2620232007
Horse Creek520191970
Auburn519791970
Crescent Cty420221972
Bass Lake420091978
Fairfax420241972
Niland420241974
Dorris420191972
Clear Lk Res420181972
Redwood N.P.420101995
Ivanpah320072007
Lake Berryessa320242023
Arvin320211988
Atwater320121972
Jackson319861973
Coyote320241972

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 2026-05-22.