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Species · Montana · BBS 2025 Release · 1966–2024

Nashville Warbler Population Trend in Montana

All statesForest birds

Nashville Warbler in Montana has surged: up 444% on the route-weighted index since 1981.

+444%Since 1981TrendPercent 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 →
23Routes 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 →
45YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Nashville Warbler Trends in MontanaNotable 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 →

Nashville Warbler has surged in Montana: up 444% on the route-weighted index since 1981.

Nashville Warbler Population Forecast in Montana

If the recent trend holds, Nashville Warbler in Montana is projected to fall about 19% by 2029 — from 0.22 in 2024 to a central estimate of 0.18 (95% range 0.05–0.31). A 5-year backtest shows a typical error of ±27.2%, with 80% of held-out values landing inside the 95% band.

-19%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 →
0.18Projected 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 →
0.05–0.3195% 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 →
±27.2%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, Nashville Warbler in Montana is projected to fall about 19% by 2029 — from 0.22 in 2024 to a central estimate of 0.18 (95% range 0.05–0.31). A 5-year backtest shows a typical error of ±27.2%, with 80% of held-out values landing inside the 95% band.19752029
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 →
20250.170.040.30
20260.170.040.31
20270.180.050.31
20280.180.050.31
20290.180.050.31

Nashville Warbler Survey Routes in Montana

Routes recording Nashville Warbler in Montana.
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 →
Fish Creek620241996
Noxon420232000
Libby Dam320241983
Kalispell220232015
Victor220212010
Threemile Wa220242010
Cramer Creek220182017
Arlee220241984
Woodman220241975
Lima220011999
St Mary119891989
Elevation Mt120182018
St Regis120241980
Clinton119841981
Sula119901987
Skalkho-Rye120222018
Swan Lake120242017
Greenoagh 3120222018
Thompson Riv120241996
Ninemile120241993
Pagil Gulch120152015
Painted Rock119961992
Wise River120121993

Nashville Warbler Population Trend in Other States

californiaconnecticutidahomainemarylandmassachusettsmichiganminnesotanew-hampshirenew-jerseynew-yorknorth-dakotaoregonpennsylvaniarhode-islandvermontvirginiawashingtonwest-virginiawisconsin

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