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Species · Maryland · BBS 2026 Release · 1966–2025

Least Bittern Population Trend in Maryland

All statesWetland birds

Least Bittern in Maryland has surged: up 169% on the route-weighted index since 1969.

+169%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 →
4Routes 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 →
48YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Least Bittern Trends in MarylandNotable 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 Least Bittern in Maryland. See the full index history below.

Least Bittern Population Forecast in Maryland

If the recent trend holds, Least Bittern in Maryland is projected to fall about 32% by 2030 — from 0.13 in 2025 to a central estimate of 0.09 (95% range 0.01–0.17). A 5-year backtest shows a typical error of ±67.4%, with 100% of held-out values landing inside the 95% band.

-32%Change by 2030TrendPercent 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 →
0.09Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.01–0.1795% 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 →
±67.4%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, Least Bittern in Maryland is projected to fall about 32% by 2030 — from 0.13 in 2025 to a central estimate of 0.09 (95% range 0.01–0.17). A 5-year backtest shows a typical error of ±67.4%, with 100% of held-out values landing inside the 95% band.19662030
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 →
20260.090.000.17
20270.090.000.17
20280.090.000.17
20290.090.010.17
20300.090.010.17

Least Bittern Survey Routes in Maryland

Routes recording Least Bittern in Maryland.
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 →
Madison320251966
Honga220251968
Golden Hill119691969
Cokesbury120221976

Least Bittern Population Trend in Other States

alabamaarizonaarkansascaliforniaconnecticutdelawarefloridageorgiaillinoisindianaiowakansaslouisianamichiganminnesotamississippimissourinebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooregonsouth-carolinasouth-dakotatexasvermontvirginiawisconsin

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.