BirdAnalyst
Species · Vermont · BBS 2025 Release · 1966–2024

Mourning Warbler Population Trend in Vermont

All statesForest birds

Mourning Warbler in Vermont has surged: up 502% on the route-weighted index since 1969.

+502%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 →
25Routes 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 →
51YearsYears 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 VermontNotable 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 surged in Vermont: up 502% on the route-weighted index since 1969.

Mourning Warbler Population Forecast in Vermont

If the recent trend holds, Mourning Warbler in Vermont is projected to rise about 93% by 2029 — from 0.33 in 2024 to a central estimate of 0.64 (95% range 0.14–1.1). A 5-year backtest shows a typical error of ±156.4%, with 80% of held-out values landing inside the 95% band.

+93%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 →
0.64Projected 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 →
0.14–1.195% 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 →
±156.4%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, Mourning Warbler in Vermont is projected to rise about 93% by 2029 — from 0.33 in 2024 to a central estimate of 0.64 (95% range 0.14–1.1). A 5-year backtest shows a typical error of ±156.4%, with 80% of held-out values landing inside the 95% band.19672029
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 →
20250.620.111.1
20260.620.121.1
20270.630.121.1
20280.640.131.1
20290.640.141.1

Mourning Warbler Survey Routes in Vermont

Routes recording Mourning Warbler in Vermont.
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 →
Gaysville220091980
S Wallingfrd219911991
East Haven220241980
Hardwick220241980
Waterville219801973
Newbury 2220232010
North Pownal119921992
Stratton120071997
Landgrove120221969
S Reading120001975
Post Mills120111977
Shaftsbury120001988
W Rutland120241989
St Johnsbury120241971
Northfld Fls120181980
Middlesex120221977
East Calais120221975
Newbury120041988
Greensboro120211967
Fletcher120231983
Hinesburg119901990
Colchester119901990
Grand Isle119971989
Stowe120231990
Bristol119961996

Mourning Warbler Population Trend in Other States

connecticutillinoisindianamainemarylandmassachusettsmichiganminnesotanew-hampshirenew-yorknorth-dakotaohiopennsylvaniawest-virginiawisconsin

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