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

Grace's Warbler Population Trend in Colorado

All statesForest birds

Grace's Warbler in Colorado has surged: up 151% on the route-weighted index since 1980.

+151%Since 1980TrendPercent 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 →
18Routes 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 →
33YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Grace'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 →

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 →

Grace's Warbler has surged in Colorado: up 151% on the route-weighted index since 1980.

Grace's Warbler Population Forecast in Colorado

If the recent trend holds, Grace's Warbler in Colorado is projected to fall about 24% by 2029 — from 0.42 in 2024 to a central estimate of 0.32 (95% range 0.16–0.49). A 5-year backtest shows a typical error of ±21.6%, with 80% of held-out values landing inside the 95% band.

-24%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 →
0.32Projected 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 →
0.16–0.4995% 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 →
±21.6%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, Grace's Warbler in Colorado is projected to fall about 24% by 2029 — from 0.42 in 2024 to a central estimate of 0.32 (95% range 0.16–0.49). A 5-year backtest shows a typical error of ±21.6%, with 80% of held-out values landing inside the 95% band.19692029
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 →
20250.310.140.47
20260.310.150.47
20270.320.150.48
20280.320.160.48
20290.320.160.49

Grace's Warbler Survey Routes in Colorado

Routes recording Grace'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 →
Mcphee Res.1620241997
Haycamp Mesa1620241998
Nucla620242000
Pagosa Spgs519751975
Cortez 2420152010
Cokedale220242019
Walsenburg220032003
Delta220212011
Dolores219691969
Cortez220061997
Blackhead Pk219981998
Animas119961996
Ludlow120142009
Uncompahgre120241999
Colona119801980
Pinon120232013
Powderhorn120232008
Piedra120151992

Grace's Warbler Population Trend in Other States

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