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

Great Blue Heron Population Trend in Pennsylvania

All statesWetland birds

Great Blue Heron in Pennsylvania has surged: up 343% on the route-weighted index since 1968.

+343%Since 1968TrendPercent 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 →
124Routes 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 →
58YearsYears 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 PennsylvaniaNotable 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 Pennsylvania: up 343% on the route-weighted index since 1968.

Great Blue Heron Population Forecast in Pennsylvania

If the recent trend holds, Great Blue Heron in Pennsylvania is projected to rise about 58% by 2029 — from 0.67 in 2024 to a central estimate of 1.1 (95% range 0.75–1.4). A 5-year backtest shows a typical error of ±38.4%, with 40% of held-out values landing inside the 95% band.

+58%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 →
1.1Projected 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 →
0.75–1.495% 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 →
±38.4%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 Pennsylvania is projected to rise about 58% by 2029 — from 0.67 in 2024 to a central estimate of 1.1 (95% range 0.75–1.4). A 5-year backtest shows a typical error of ±38.4%, with 40% of held-out values landing inside the 95% band.19662029
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 →
20251.00.691.3
20261.00.711.3
20271.00.721.4
20281.10.731.4
20291.10.751.4

Great Blue Heron Survey Routes in Pennsylvania

Routes recording Great Blue Heron in Pennsylvania.
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 →
Beaver520231984
Teepleville420241967
Plesant Grov420221969
Drehersville419981986
Akron419971997
Mt Gretna 2420182001
Drehersville 2420242001
Shrewsbury420191991
N Washington320221973
Canadensis320241998
Parkwood320241998
Mifflintown320231980
Brunnerville320091974
Brunnerville 2320242010
Bendersville320241993
Slippery Rk219941970
Clover220241988
Akeley219731966
Arnot220241972
Logue220221980
English Ctr219731968
Rush220241970
Susquehanna220241972
Duvall220211982
Kaylor220231997

Great Blue Heron Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonrhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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