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

Great Blue Heron Population Trend in Colorado

All statesWetland birds

Great Blue Heron in Colorado has surged: up 219% on the route-weighted index since 1973.

+219%Since 1973TrendPercent 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 →
98Routes 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 →
52YearsYears 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 ColoradoNotable 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 Colorado: up 219% on the route-weighted index since 1973.

Great Blue Heron Population Forecast in Colorado

If the recent trend holds, Great Blue Heron in Colorado is projected to rise about 116% by 2029 — from 0.26 in 2024 to a central estimate of 0.56 (95% range 0.19–0.92). A 5-year backtest shows a typical error of ±117%, with 60% of held-out values landing inside the 95% band.

+116%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 →
0.56Projected 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 →
0.19–0.9295% 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 →
±117%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 Colorado is projected to rise about 116% by 2029 — from 0.26 in 2024 to a central estimate of 0.56 (95% range 0.19–0.92). A 5-year backtest shows a typical error of ±117%, with 60% of held-out values landing inside the 95% band.19712029
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 →
20250.530.170.90
20260.540.170.90
20270.540.180.91
20280.550.180.92
20290.560.190.92

Great Blue Heron Survey Routes in Colorado

Routes recording Great Blue Heron in Colorado.
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 →
Buford1120231972
Fleming920031992
Wildhorse L520001991
Cokedale520242007
Cochetopa Pass520222001
Gilpin420161999
Walden420191999
Cortez420071993
Stillwater Pass 2420162012
Hudson320241989
Browns Park320151995
Grover320131999
Haswell319991993
Neegrande320191995
Flagler320031997
Elbert320192000
Yampa220181971
Harmony220191974
Pinneo219931973
Aspen220241993
Cheesman Lk220161995
Moffat220232023
Lost Lake220052005
Castleton220241991
Doyleville220241988

Great Blue Heron Population Trend in Other States

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

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