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Species · Massachusetts · BBS 2025 Release · 1966–2024

Black-crowned Night Heron Population Trend in Massachusetts

All statesWetland birds

Black-crowned Night Heron in Massachusetts has declined: down 39% on the route-weighted index since 1969.

-39%Since 1969TrendPercent 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 →
9Routes 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 →
34YearsYears 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 MassachusettsNotable 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 Massachusetts. See the full index history below.

Black-crowned Night Heron Population Forecast in Massachusetts

If the recent trend holds, Black-crowned Night Heron in Massachusetts is projected to fall about 72% by 2026 — from 0.16 in 2021 to a central estimate of 0.04 (95% range 0.00–0.48). A 5-year backtest shows a typical error of ±36.9%, with 100% of held-out values landing inside the 95% band.

-72%Change by 2026TrendPercent 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 →
0.04Projected 2026 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.4895% 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 →
±36.9%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 Massachusetts is projected to fall about 72% by 2026 — from 0.16 in 2021 to a central estimate of 0.04 (95% range 0.00–0.48). A 5-year backtest shows a typical error of ±36.9%, with 100% of held-out values landing inside the 95% band.19672026
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 →
20220.060.000.49
20230.060.000.49
20240.050.000.48
20250.050.000.48
20260.040.000.48

Black-crowned Night Heron Survey Routes in Massachusetts

Routes recording Black-crowned Night Heron in Massachusetts.
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 →
E Dennis320211977
Maynard319731973
Marion219801980
Warren219701970
Chilmark119801969
Brockton120011970
Newburyport120131967
Littleton119971969
Gay Head120181996

Black-crowned Night Heron Population Trend in Other States

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

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