BirdAnalyst
Species · BCR 32 · BBS 2025 Release · 1966–2024

Great Blue Heron In Coastal California

All regionsCoastal CaliforniaWetland birds

Great Blue Heron in Coastal California has risen sharply: up 70% on the route-weighted index since 1970.

+70%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 →
83Routes In RegionSurvey 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 SignalsNotable 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 increasecomputed 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 →

Great Blue Heron has risen sharply in Coastal California: up 70% on the route-weighted index since 1970.

Great Blue Heron In Coastal California Population Forecast

If the recent trend holds, Great Blue Heron in Coastal California is projected to fall about 13% by 2029 — from 1.1 in 2024 to a central estimate of 1.00 (95% range 0.13–1.9). A 5-year backtest shows a typical error of ±56.6%, with 100% of held-out values landing inside the 95% band.

-13%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 →
1.00Projected 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 →
0.13–1.995% 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 →
±56.6%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, Great Blue Heron in Coastal California is projected to fall about 13% by 2029 — from 1.1 in 2024 to a central estimate of 1.00 (95% range 0.13–1.9). A 5-year backtest shows a typical error of ±56.6%, with 100% 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 →
20251.00.151.9
20261.00.141.9
20271.00.141.9
20281.00.131.9
20291.000.131.9

Routes In Coastal California

Routes recording Great Blue Heron in Coastal 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 →
HollisterCALIFORNIA102007
Staten Is.CALIFORNIA82024
HughsonCALIFORNIA72024
ShafterCALIFORNIA71988
GlennCALIFORNIA72023
Ora LomaCALIFORNIA72024
Lake SuccessCALIFORNIA61981
Collegeville 2CALIFORNIA62023
AuburnCALIFORNIA51979
FairfaxCALIFORNIA42024
Lake BerryessaCALIFORNIA32024
ArvinCALIFORNIA32021
AtwaterCALIFORNIA32012
JacksonCALIFORNIA31986
CoyoteCALIFORNIA32024
PolomaCALIFORNIA32021
CalpellaCALIFORNIA21986
RumseyCALIFORNIA22007
BakersfieldCALIFORNIA22015
AdelaidaCALIFORNIA22024
SangerCALIFORNIA22024
CrestonCALIFORNIA22024
White RiverCALIFORNIA21992
CordovaCALIFORNIA21981
Gold HillCALIFORNIA22024

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