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

Great Blue Heron Population Trend in Massachusetts

All statesWetland birds

Great Blue Heron in Massachusetts has surged: up 13× on the route-weighted index since 1969.

13×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 →
28Routes 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 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 13× 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 fall about 18% by 2029 — from 1.1 in 2024 to a central estimate of 0.93 (95% range 0.59–1.3). A 5-year backtest shows a typical error of ±27.1%, with 40% of held-out values landing inside the 95% band.

-18%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 →
0.93Projected 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 →
0.59–1.395% 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 →
±27.1%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 fall about 18% by 2029 — from 1.1 in 2024 to a central estimate of 0.93 (95% range 0.59–1.3). A 5-year backtest shows a typical error of ±27.1%, with 40% of held-out values landing inside the 95% band.19672029
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 →
20250.870.531.2
20260.890.551.2
20270.900.561.2
20280.920.581.3
20290.930.591.3

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 →
Warren 2620232010
Marion520241969
Brockton520191968
N. Andover520241999
Holden320241985
Ware River220221994
E Pepperell219941967
Cheshire219911991
Hancock220112010
E Dennis120181969
Chilmark119831973
Prattville120182005
Newburyport120221974
Maynard120221989
Littleton120221989
N Oxford120241996
Mansfield120241990
Princeton119741974
Belchertown120231991
Warren120091985
S Barre120241977
N Orange120241970
Cummington120062000
Chesterfield120211970
Pittsfield119981998

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 2026-05-22.