BirdAnalyst
Species · New Hampshire · BBS 2026 Release · 1966–2025

Mourning Warbler Population Trend in New Hampshire

All statesForest birds

Mourning Warbler in New Hampshire has risen sharply: up 67% on the route-weighted index since 1969.

+67%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 →
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 →
55YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Mourning 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 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 →

Mourning Warbler has risen sharply in New Hampshire: up 67% on the route-weighted index since 1969.

Mourning Warbler Population Forecast in New Hampshire

If the recent trend holds, Mourning Warbler in New Hampshire is projected to stay roughly flat through 2030, near 0.22 (95% range 0.00–0.48). A 5-year backtest shows a typical error of ±24.5%, with 100% of held-out values landing inside the 95% band.

+0%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 →
0.22Projected 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 →
0.00–0.4895% 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 →
±24.5%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, Mourning Warbler in New Hampshire is projected to stay roughly flat through 2030, near 0.22 (95% range 0.00–0.48). A 5-year backtest shows a typical error of ±24.5%, 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 →
20260.210.000.47
20270.210.000.47
20280.210.000.47
20290.220.000.48
20300.220.000.48

Mourning Warbler Survey Routes in New Hampshire

Routes recording Mourning 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 →
Marlow220182018
Dixvil Notch220171971
Dixville Notch 2220252018
Hopkinton120172010
Wilmot120252010
Jefferson Hl120231966
Franconia120121966
Milan120231966
Stratford120251966
Clarksville120251969
Glen120221996
Jeffers Ntch120101996

Mourning Warbler Population Trend in Other States

connecticutillinoisindianamainemarylandmassachusettsmichiganminnesotanew-yorknorth-dakotaohiopennsylvaniavermontwest-virginiawisconsin

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