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Species · Montana · BBS 2026 Release · 1966–2025

MacGillivray's Warbler Population Trend in Montana

All statesForest birds

MacGillivray's Warbler in Montana has surged: up 95% on the route-weighted index since 1970.

+95%Since 1970TrendPercent 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 →
47Routes 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 →
57YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable MacGillivray's 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 →

MacGillivray's Warbler has surged in Montana: up 95% on the route-weighted index since 1970.

MacGillivray's Warbler Population Forecast in Montana

If the recent trend holds, MacGillivray's Warbler in Montana is projected to rise about 86% by 2030 — from 2.0 in 2025 to a central estimate of 3.7 (95% range 1.9–5.5). A 5-year backtest shows a typical error of ±108%, with 0% of held-out values landing inside the 95% band.

+86%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 →
3.7Projected 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 →
1.9–5.595% 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 →
±108%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, MacGillivray's Warbler in Montana is projected to rise about 86% by 2030 — from 2.0 in 2025 to a central estimate of 3.7 (95% range 1.9–5.5). A 5-year backtest shows a typical error of ±108%, with 0% of held-out values landing inside the 95% band.19682030
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 →
20263.61.85.4
20273.61.85.4
20283.61.95.4
20293.71.95.5
20303.71.95.5

MacGillivray's Warbler Survey Routes in Montana

Routes recording MacGillivray's 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 Creek2420241995
Woodman2120251970
Logan Pass1920251980
Skalkaho1919981992
Clinton1620251975
Whitefish Lake1520242016
St Regis1420251977
East Glacier Park1320252015
Noxon1220231995
Threemile Wa1120251993
Ninemile1120251993
Hebgen Lake1120252017
Greenoagh 21020112005
Painted Rock920221992
Wise River920251993
Sula820241978
Cramer Creek720191995
Pryor Mtn.720251995
Swan Lake620252015
Inside Road520251990
Thompson Riv520241993
Kalispell420251969
Red Rock420251981
Clancy420252015
Victor320251993

MacGillivray's Warbler Population Trend in Other States

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