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

Great-tailed Grackle Population Trend in Colorado

All statesGeneralists

Great-tailed Grackle in Colorado has surged: up 239% on the route-weighted index since 1984.

+239%Since 1984TrendPercent 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 →
40Routes 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 Great-tailed Grackle 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 →

Great-tailed Grackle has surged in Colorado: up 239% on the route-weighted index since 1984.

Great-tailed Grackle Population Forecast in Colorado

If the recent trend holds, Great-tailed Grackle in Colorado is projected to rise about 106% by 2029 — from 0.34 in 2024 to a central estimate of 0.70 (95% range 0.27–1.1). A 5-year backtest shows a typical error of ±46%, with 80% of held-out values landing inside the 95% band.

+106%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 →
0.70Projected 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 →
0.27–1.195% 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 →
±46%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, Great-tailed Grackle in Colorado is projected to rise about 106% by 2029 — from 0.34 in 2024 to a central estimate of 0.70 (95% range 0.27–1.1). A 5-year backtest shows a typical error of ±46%, with 80% of held-out values landing inside the 95% band.19822029
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 →
20250.650.221.1
20260.660.231.1
20270.680.251.1
20280.690.261.1
20290.700.271.1

Great-tailed Grackle Survey Routes in Colorado

Routes recording Great-tailed Grackle 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 →
Bethune3120182001
Doyle Bridge 21720221998
Doyle Bridge1219971996
Prospect Valley 2920102001
Pritchett720192007
Edler720242003
Lamar620231995
Fort Morgan620242000
Campo620192000
Flagler520241997
Limon520222015
Dolores419871982
Alamosa420241997
Cone Mtn420072007
Fleming320232005
Rush320242024
Cheyenne320241998
Burlington320242008
Gilpin220242017
Hudson220212000
Cortez 2220142013
Nunn220212016
Julesburg220211998
Ellicott220232013
Grover220182018

Great-tailed Grackle Population Trend in Other States

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