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

Great Blue Heron Population Trend in Massachusetts

All statesWetland birds

Great Blue Heron in Massachusetts has surged: up 12× on the route-weighted index since 1969.

12×Since 1969TrendPercent 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 →
29Routes 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 MassachusettsNotable 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 surged in Massachusetts: up 12× on the route-weighted index since 1969.

Great Blue Heron Population Forecast in Massachusetts

If the recent trend holds, Great Blue Heron in Massachusetts is projected to rise about 17% by 2030 — from 0.81 in 2025 to a central estimate of 0.95 (95% range 0.61–1.3). A 5-year backtest shows a typical error of ±23%, with 80% of held-out values landing inside the 95% band.

+17%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 →
0.95Projected 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 →
0.61–1.395% 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 →
±23%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 Massachusetts is projected to rise about 17% by 2030 — from 0.81 in 2025 to a central estimate of 0.95 (95% range 0.61–1.3). A 5-year backtest shows a typical error of ±23%, with 80% of held-out values landing inside the 95% band.19672030
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 →
20260.880.541.2
20270.900.561.2
20280.910.571.3
20290.930.591.3
20300.950.611.3

Great Blue Heron Survey Routes in Massachusetts

Routes recording Great Blue Heron in Massachusetts.
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 →
Marion520251969
Brockton520191968
Ware River220221994
E Pepperell219941967
Cheshire219911991
Warren 2220252010
Hancock220112010
E Dennis120181969
Chilmark119831973
Prattville120182005
Newburyport120221974
Maynard120251989
Littleton120221989
N Oxford120241996
Mansfield120241990
Princeton119741974
Belchertown120231991
Warren120091985
S Barre120241977
N Orange120251970
Cummington120062000
Chesterfield120211970
Pittsfield119981998
Sheffield120121992
Monterey120252021

Great Blue Heron Population Trend in Other States

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

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