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

Gray Vireo Population Trend in Colorado

All statesForest birds

Gray Vireo in Colorado has surged: up 374% on the route-weighted index since 1976.

+374%Since 1976TrendPercent 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 →
25Routes 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 →
39YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Gray Vireo 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 →

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 →

Gray Vireo has surged in Colorado: up 374% on the route-weighted index since 1976.

Gray Vireo Population Forecast in Colorado

If the recent trend holds, Gray Vireo in Colorado is projected to fall about 16% by 2029 — from 0.17 in 2024 to a central estimate of 0.15 (95% range 0.05–0.25). A 5-year backtest shows a typical error of ±43.8%, with 20% of held-out values landing inside the 95% band.

-16%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 →
0.15Projected 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 →
0.05–0.2595% 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 →
±43.8%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, Gray Vireo in Colorado is projected to fall about 16% by 2029 — from 0.17 in 2024 to a central estimate of 0.15 (95% range 0.05–0.25). A 5-year backtest shows a typical error of ±43.8%, with 20% of held-out values landing inside the 95% band.19742029
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 →
20250.140.040.23
20260.140.040.24
20270.140.040.24
20280.140.050.24
20290.150.050.25

Gray Vireo Survey Routes in Colorado

Routes recording Gray Vireo 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 →
Animas720041996
Mesaverde Np520242003
Rosevale520232013
Baxter Pass320241995
Angora320242001
Blackhead Pk320002000
Maybell220232016
Douglas Pass220241988
Falfa219911991
Wray Gulch220192005
Dinosaur220232001
Villegreen220242006
Basin220232014
Radium219981998
Nucla220242000
Delta120161974
Wilson Creek120182018
Cortez 2120132013
Animas 2120172005
Lay120172017
Trinchera120212021
De Beque120182009
Pinon120232023
Ninaview120102010
Gardner120002000

Gray Vireo Population Trend in Other States

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