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Species · Connecticut · BBS 2025 Release · 1966–2024

Black-crowned Night Heron Population Trend in Connecticut

All statesWetland birds

Black-crowned Night Heron in Connecticut has held roughly steady: down 5% on the route-weighted index since 1980.

-5%Since 1980TrendPercent 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 →
6Routes 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 →
19YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Black-crowned Night 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 →

No notable trend signals for Black-crowned Night Heron in Connecticut. See the full index history below.

Black-crowned Night Heron Population Forecast in Connecticut

If the recent trend holds, Black-crowned Night Heron in Connecticut is projected to fall about 13% by 2020 — from 0.29 in 2015 to a central estimate of 0.25 (95% range 0.00–0.56). A 5-year backtest shows a typical error of ±150.4%, with 100% of held-out values landing inside the 95% band.

-13%Change by 2020TrendPercent 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 →
0.25Projected 2020 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.5695% 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 →
±150.4%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, Black-crowned Night Heron in Connecticut is projected to fall about 13% by 2020 — from 0.29 in 2015 to a central estimate of 0.25 (95% range 0.00–0.56). A 5-year backtest shows a typical error of ±150.4%, with 100% of held-out values landing inside the 95% band.19692020
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 →
20160.240.000.55
20170.240.000.56
20180.240.000.56
20190.250.000.56
20200.250.000.56

Black-crowned Night Heron Survey Routes in Connecticut

Routes recording Black-crowned Night 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 →
Westbrook220151969
Mystic120131980
E Hartland119831983
Buckingham119851985
Greenwich120151979
Long Hill120152015

Black-crowned Night Heron Population Trend in Other States

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

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