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

Northern Harrier Population Trend in Colorado

All statesGeneralists

Northern Harrier in Colorado has collapsed: down 83% on the route-weighted index since 1970.

-83%Since 1970
85Routes In State
56Years

Notable Northern Harrier Trends in Colorado

long arc declinecomputed index

Northern Harrier has collapsed in Colorado: down 83% on the route-weighted index since 1970.

Northern Harrier Population Forecast in Colorado

If the recent trend holds, Northern Harrier in Colorado is projected to fall about 61% by 2029 — from 0.19 in 2024 to a central estimate of 0.07 (95% range 0.00–0.43). A 5-year backtest shows a typical error of ±33.2%, with 100% of held-out values landing inside the 95% band.

-61%Change by 2029
0.07Projected 2029 index
0.00–0.4395% range
±33.2%Backtest error
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 index95% low95% high
20250.110.000.47
20260.100.000.46
20270.090.000.45
20280.080.000.44
20290.070.000.43

Northern Harrier Survey Routes in Colorado

Routes recording Northern Harrier in Colorado.
Adams Co.520211989
Great Divide320241976
Briggsdale320211968
Gilpin320111975
Waverly320191995
Cheyenne320181992
Last Chance 2320242017
Prospect Val320001992
Mosca320051992
Prospect Valley 2320222001
Pinneo220181980
Douglas Pass220232003
Abarr219991968
Moffat220151970
Two Buttes220091974
Wildhorse L220241989
Gordon Creek220221988
Pleasant View220212021
San Luis220091991
Browns Park220151994
Kirk220231993
Ninaview220042000
Timpas220061998
Mesita220082008
Maybell120241970

Northern Harrier Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniadelawaregeorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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