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

Northern Harrier Population Trend in Wisconsin

All statesGeneralists

Northern Harrier in Wisconsin has fallen sharply: down 52% on the route-weighted index since 1968.

-52%Since 1968
83Routes In State
58Years

Notable Northern Harrier Trends in Wisconsin

long arc declinecomputed index

Northern Harrier has fallen sharply in Wisconsin: down 52% on the route-weighted index since 1968.

Northern Harrier Population Forecast in Wisconsin

If the recent trend holds, Northern Harrier in Wisconsin is projected to stay roughly flat through 2029, near 0.25 (95% range 0.05–0.45). A 5-year backtest shows a typical error of ±199.2%, with 40% of held-out values landing inside the 95% band.

n/aChange by 2029
0.25Projected 2029 index
0.05–0.4595% range
±199.2%Backtest error
19662029
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
20250.260.060.45
20260.250.060.45
20270.250.060.45
20280.250.060.45
20290.250.050.45

Northern Harrier Survey Routes in Wisconsin

Routes recording Northern Harrier in Wisconsin.
Bayfield220191978
Dresser220221966
Loraine220181966
Phillips220221969
Merrill220231969
Rolling Pr220171966
Raymond219801980
Meridean220092009
Buena Vista220221998
Annaton220212003
Chaffey119951968
Iron River120161967
Minong120181969
Shanagolden119791972
Hudson120231967
Union Twp119861986
Cumberland120141966
Weyerhauser120221967
Couderay120011975
Exeland120221971
Gilman120171976
Holway119881968
Rib Lake120211975
Irma120221969
Mcnaughton119921992

Northern Harrier Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradodelawaregeorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawyoming

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