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

Mourning Warbler Population Trend in New Hampshire

All statesForest birds

Mourning Warbler in New Hampshire has risen sharply: up 69% on the route-weighted index since 1969.

+69%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 →
54YearsYears 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 69% 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 fall about 21% by 2029 — from 0.27 in 2024 to a central estimate of 0.22 (95% range 0.00–0.48). A 5-year backtest shows a typical error of ±89.2%, with 100% of held-out values landing inside the 95% band.

-21%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 →
0.22Projected 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 →
0.00–0.4895% 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 →
±89.2%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 fall about 21% by 2029 — from 0.27 in 2024 to a central estimate of 0.22 (95% range 0.00–0.48). A 5-year backtest shows a typical error of ±89.2%, 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 →
20250.210.000.47
20260.210.000.48
20270.210.000.48
20280.220.000.48
20290.220.000.48

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 →
Dixville Notch 2620242018
Marlow220182018
Dixvil Notch220171971
Hopkinton120172010
Wilmot120162010
Jefferson Hl120231966
Franconia120121966
Milan120231966
Stratford120231966
Clarksville120231969
Glen120221996
Jeffers Ntch120101996

Mourning Warbler Population Trend in Other States

connecticutillinoisindianamainemarylandmassachusettsmichiganminnesotanew-yorknorth-dakotaohiopennsylvaniavermontwest-virginiawisconsin

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