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Species · Colorado · BBS 2026 Release · 1966–2025

MacGillivray's Warbler Population Trend in Colorado

All statesForest birds

MacGillivray's Warbler in Colorado has edged up: up 19% on the route-weighted index since 1970.

+19%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 →
81Routes 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 ColoradoNotable 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 MacGillivray's Warbler in Colorado. See the full index history below.

MacGillivray's Warbler Population Forecast in Colorado

If the recent trend holds, MacGillivray's Warbler in Colorado is projected to fall about 12% by 2030 — from 1.8 in 2025 to a central estimate of 1.6 (95% range 0.76–2.4). A 5-year backtest shows a typical error of ±13.5%, with 100% of held-out values landing inside the 95% band.

-12%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 →
1.6Projected 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 →
0.76–2.495% 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 →
±13.5%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 Colorado is projected to fall about 12% by 2030 — from 1.8 in 2025 to a central estimate of 1.6 (95% range 0.76–2.4). A 5-year backtest shows a typical error of ±13.5%, with 100% 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 →
20261.60.712.4
20271.60.722.4
20281.60.732.4
20291.60.742.4
20301.60.762.4

MacGillivray's Warbler Survey Routes in Colorado

Routes recording MacGillivray's Warbler in Colorado.
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 →
Yampa1620231970
Aspen1320251979
Uncompahgre1220251988
Dunckley Pas1220251992
Flattops1220251994
Blackhead Pk1020251993
Thomasville1020251992
Marshall Pas1020141998
Dolores Riv920251988
Mcphee Res.920251998
Douglas Pass820241982
Heeney820192019
Red Cliff720251989
Baxter Pass720241994
Angora720251998
Nucla720251999
Wilson Creek620251992
Deadman Rd.620251997
Comanche Pk620241996
Yellowjacket Pass620251998
Steamboat L.520251996
Heeney 2520252025
Parlin420231968
Lost Lake420251990
Tarryall420252000

MacGillivray's Warbler Population Trend in Other States

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