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

Great Blue Heron Population Trend in Connecticut

All statesWetland birds

Great Blue Heron in Connecticut has surged: up 768% on the route-weighted index since 1975.

+768%Since 1975TrendPercent 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 →
18Routes 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 →
49YearsYears 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 ConnecticutNotable 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 Connecticut: up 768% on the route-weighted index since 1975.

Great Blue Heron Population Forecast in Connecticut

If the recent trend holds, Great Blue Heron in Connecticut is projected to rise about 103% by 2029 — from 0.56 in 2024 to a central estimate of 1.1 (95% range 0.57–1.7). A 5-year backtest shows a typical error of ±37.1%, with 80% of held-out values landing inside the 95% band.

+103%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 →
0.57–1.795% 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 →
±37.1%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 Connecticut is projected to rise about 103% by 2029 — from 0.56 in 2024 to a central estimate of 1.1 (95% range 0.57–1.7). A 5-year backtest shows a typical error of ±37.1%, with 80% of held-out values landing inside the 95% band.19732029
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 →
20251.00.491.6
20261.10.511.6
20271.10.531.6
20281.10.551.7
20291.10.571.7

Great Blue Heron Survey Routes in Connecticut

Routes recording Great Blue Heron in Connecticut.
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 →
Woodstock320071976
Buckingham220141993
Uncasville220231999
Willimantic220141991
Danbury220232006
Southington220242008
Warren 2220152012
Mystic120231973
New Hartford120231994
Westbrook120241991
No Woodbury120141983
Sherman120191985
Greenwich119831983
Warren120111993
Long Hill120191975
Mid Haddam120241973
Woodstock 2120242017
Granby120231988

Great Blue Heron Population Trend in Other States

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

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