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Species · Montana · BBS 2025 Release · 1966–2024

MacGillivray's Warbler Population Trend in Montana

All statesForest birds

MacGillivray's Warbler in Montana has surged: up 101% on the route-weighted index since 1970.

+101%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 →
56YearsYears 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 100% 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 80% by 2029 — from 2.1 in 2024 to a central estimate of 3.8 (95% range 2.1–5.5). A 5-year backtest shows a typical error of ±106.4%, with 0% of held-out values landing inside the 95% band.

+80%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 →
3.8Projected 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 →
2.1–5.595% 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 →
±106.4%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, MacGillivray's Warbler in Montana is projected to rise about 80% by 2029 — from 2.1 in 2024 to a central estimate of 3.8 (95% range 2.1–5.5). A 5-year backtest shows a typical error of ±106.4%, with 0% of held-out values landing inside the 95% band.19682029
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 →
20253.71.95.4
20263.72.05.5
20273.72.05.5
20283.82.05.5
20293.82.15.5

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
Skalkaho1919981992
Logan Pass1820241980
Whitefish Lake1520242016
Clinton1320241975
Noxon1220231995
Arlee1120241968
Greenoagh 21020112005
Libby Dam920241979
Woodman920241970
Painted Rock920221992
Sula820241978
Swan Lake820242015
Cramer Creek720191995
Inside Road720241990
Hebgen Lake720242017
St Regis620241977
Ninemile620241993
East Glacier Park520242015
Greenoagh 3520242012
Thompson Riv520241993
Lima420241994
Threemile Wa320241993
Elevation Mt320241995
Pryor Mtn.320241995

MacGillivray's Warbler Population Trend in Other States

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