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

Great Blue Heron Population Trend in Delaware

All statesWetland birds

Great Blue Heron in Delaware has surged: up 34× on the route-weighted index since 1968.

34×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 →
17Routes 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 DelawareNotable 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 Delaware: up 34× on the route-weighted index since 1968.

Great Blue Heron Population Forecast in Delaware

If the recent trend holds, Great Blue Heron in Delaware is projected to fall about 50% by 2029 — from 12 in 2024 to a central estimate of 6.2 (95% range 3.9–8.5). A 5-year backtest shows a typical error of ±24%, with 60% of held-out values landing inside the 95% band.

-50%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 →
6.2Projected 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 →
3.9–8.595% 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 →
±24%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 Delaware is projected to fall about 50% by 2029 — from 12 in 2024 to a central estimate of 6.2 (95% range 3.9–8.5). A 5-year backtest shows a typical error of ±24%, with 60% 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 →
20255.83.58.1
20265.93.68.2
20276.03.78.3
20286.13.88.4
20296.23.98.5

Great Blue Heron Survey Routes in Delaware

Routes recording Great Blue Heron in Delaware.
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 →
Harrington3820241968
Blackbird2320241994
Lowes Xrds1319911967
Holleyville720041967
Mt Pleasant520191967
Pepperbox 2520232017
Holleyville 2420182006
Wilmington320141971
Pepperbox320161998
Frederica220131969
Dover219871974
Frankford220121969
Bethany Bch219901966
Milton220161985
Millsboro120242017
Georgetown120181992
Milton 2120172017

Great Blue Heron Population Trend in Other States

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

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