BirdAnalyst
Species · New Hampshire · BBS 2025 Release · 1966–2024

Bay-breasted Warbler Population Trend in New Hampshire

All statesForest birds

Bay-breasted Warbler in New Hampshire has collapsed: down 82% on the route-weighted index since 1968.

-82%Since 1968TrendPercent 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 →
12Routes 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 →
50YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Bay-breasted Warbler Trends in New HampshireNotable 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 declinecomputed 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 →

Bay-breasted Warbler has collapsed in New Hampshire: down 82% on the route-weighted index since 1968.

Bay-breasted Warbler Population Forecast in New Hampshire

If the recent trend holds, Bay-breasted Warbler in New Hampshire is projected to stay roughly flat through 2029, near 0.00 (95% range 0.00–0.30). A 5-year backtest shows a typical error of ±93.1%, with 100% of held-out values landing inside the 95% band.

n/aChange 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 →
0.00Projected 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 →
0.00–0.3095% 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 →
±93.1%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, Bay-breasted Warbler in New Hampshire is projected to stay roughly flat through 2029, near 0.00 (95% range 0.00–0.30). A 5-year backtest shows a typical error of ±93.1%, 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 →
20250.020.000.31
20260.010.000.31
20270.000.000.30
20280.000.000.30
20290.000.000.30

Bay-breasted Warbler Survey Routes in New Hampshire

Routes recording Bay-breasted Warbler in New Hampshire.
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 →
Clarksville420071966
Mt Chocorua319911973
Fitzwilliam119841984
Walpole119741974
Lempster119791979
Crawford Not119731967
Jefferson Hl120241968
Franconia119791966
Milan120001966
Stratford119751970
Dixvil Notch120081966
Glen120121976

Bay-breasted Warbler Population Trend in Other States

mainemichiganminnesotanew-yorkpennsylvaniavermontwisconsin

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