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

Northern Harrier Population Trend in Michigan

All statesGeneralists

Northern Harrier in Michigan has collapsed: down 83% on the route-weighted index since 1968.

-83%Since 1968TrendPercent 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 →
61Routes 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 →
57YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Northern Harrier Trends in MichiganNotable 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 declinecomputed 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 →

Northern Harrier has collapsed in Michigan: down 83% on the route-weighted index since 1968.

Northern Harrier Population Forecast in Michigan

If the recent trend holds, Northern Harrier in Michigan is projected to stay roughly flat through 2029, near 0.06 (95% range 0.00–0.19). A 5-year backtest shows a typical error of ±87.7%, with 100% of held-out values landing inside the 95% band.

-8%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 →
0.06Projected 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 →
0.00–0.1995% 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 →
±87.7%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, Northern Harrier in Michigan is projected to stay roughly flat through 2029, near 0.06 (95% range 0.00–0.19). A 5-year backtest shows a typical error of ±87.7%, with 100% of held-out values landing inside the 95% band.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 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 →
20250.070.000.20
20260.070.000.19
20270.060.000.19
20280.060.000.19
20290.060.000.19

Northern Harrier Survey Routes in Michigan

Routes recording Northern Harrier in Michigan.
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 →
Crystal Fls219921982
Skeels219891967
No Bradley219941970
Beaver Lake219701968
Hubbard Lake219931974
Owendale219921979
S Lyons219701966
Seney Nwr220182008
Ontonagon119671967
Hungerford119951995
Bootjack120091968
Ned Lake119881986
Chippewa Lk.120022002
Gibbs City120061999
Maple Grove120241970
Ishpeming119811981
Brocky Lake120182018
Wilson120091968
Cunard119941987
Shingleton120051967
Walloon Lake 2120082008
Isabella120041972
Bear Lake120121988
Scottville119761976
Hamburg 2120142014

Northern Harrier Population Trend in Other States

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

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