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

Cassin's Vireo Population Trend in Montana

All statesForest birds

Cassin's Vireo in Montana has held roughly steady: down 6% on the route-weighted index since 1970.

-6%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 →
33Routes 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 Cassin's Vireo 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 →

No notable trend signals for Cassin's Vireo in Montana. See the full index history below.

Cassin's Vireo Population Forecast in Montana

If the recent trend holds, Cassin's Vireo in Montana is projected to rise about 18% by 2029 — from 1.1 in 2024 to a central estimate of 1.3 (95% range 0.59–1.9). A 5-year backtest shows a typical error of ±24.6%, with 100% of held-out values landing inside the 95% band.

+18%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 →
1.3Projected 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 →
0.59–1.995% 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 →
±24.6%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, Cassin's Vireo in Montana is projected to rise about 18% by 2029 — from 1.1 in 2024 to a central estimate of 1.3 (95% range 0.59–1.9). A 5-year backtest shows a typical error of ±24.6%, with 100% 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 →
20251.20.541.9
20261.20.551.9
20271.20.561.9
20281.30.571.9
20291.30.591.9

Cassin's Vireo Survey Routes in Montana

Routes recording Cassin's Vireo 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 →
Pagil Gulch2120242015
Fish Creek1820241995
Noxon1120231995
Whitefish Lake720242016
Skalkho-Rye720222008
St Regis620241978
Woodman620241969
Greenoagh 3620242012
Libby Dam520241979
Clinton520241976
Ninemile520231993
Cramer Creek420192004
Greenough320041996
Painted Rock320191992
Kalispell220241972
Victor220241993
Elevation Mt220242005
Inside Road220241990
Sula220241998
St Mary120021968
Logan Pass120231993
Threemile Wa120241993
Polson120191989
Arlee120241968
Elliston120182014

Cassin's Vireo Population Trend in Other States

alaskacaliforniaidahooregonwashington

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