BirdAnalyst
Species · BCR 30 · BBS 2025 Release · 1966–2024

Least Bittern In New England / Mid-Atlantic Coast

All regionsNew England / Mid-Atlantic CoastWetland birds

Least Bittern in New England / Mid-Atlantic Coast has surged: up 165% on the route-weighted index since 1969.

+165%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 →
11Routes In RegionSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
49YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable SignalsNotable 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 →

Least Bittern has surged in New England / Mid-Atlantic Coast: up 165% on the route-weighted index since 1969.

Least Bittern In New England / Mid-Atlantic Coast Population Forecast

If the recent trend holds, Least Bittern in New England / Mid-Atlantic Coast is projected to stay roughly flat through 2029, near 0.05 (95% range 0.00–0.10). A 5-year backtest shows a typical error of ±22.7%, with 100% of held-out values landing inside the 95% band.

-8%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 →
0.05Projected 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 →
0.00–0.1095% 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 →
±22.7%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 New England / Mid-Atlantic Coast is projected to stay roughly flat through 2029, near 0.05 (95% range 0.00–0.10). A 5-year backtest shows a typical error of ±22.7%, with 100% 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 →
20250.050.000.10
20260.050.000.10
20270.050.000.10
20280.050.000.10
20290.050.000.10

Routes In New England / Mid-Atlantic Coast

Routes recording Least Bittern in New England / Mid-Atlantic Coast.
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 →
DanburyCONNECTICUT21976
BlackbirdDELAWARE22021
MadisonMARYLAND22024
WarrenCONNECTICUT11988
HarringtonDELAWARE12003
Golden HillMARYLAND11969
HongaMARYLAND12024
CokesburyMARYLAND12022
DoverNEW-HAMPSHIRE11973
East KingstonNEW-HAMPSHIRE12017
FriendshipNEW-JERSEY12024

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