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

Northern Harrier Population Trend in Montana

All statesGeneralists

Northern Harrier in Montana has edged down: down 11% on the route-weighted index since 1970.

-11%Since 1970TrendPercent 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 →
89Routes 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 →
56YearsYears 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 MontanaNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

No notable trend signals for Northern Harrier in Montana. See the full index history below.

Northern Harrier Population Forecast in Montana

If the recent trend holds, Northern Harrier in Montana is projected to fall about 28% by 2029 — from 1.6 in 2024 to a central estimate of 1.1 (95% range 0.41–1.8). A 5-year backtest shows a typical error of ±36.2%, with 100% of held-out values landing inside the 95% band.

-28%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 →
1.1Projected 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 →
0.41–1.895% 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 →
±36.2%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 Montana is projected to fall about 28% by 2029 — from 1.6 in 2024 to a central estimate of 1.1 (95% range 0.41–1.8). A 5-year backtest shows a typical error of ±36.2%, with 100% of held-out values landing inside the 95% band.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 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 →
20251.10.421.8
20261.10.421.8
20271.10.411.8
20281.10.411.8
20291.10.411.8

Northern Harrier Survey Routes in Montana

Routes recording Northern Harrier in Montana.
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 →
Cleveland1520241979
Two Dot920241976
Lambert720242021
Church Hill720242017
Hay Lake620221988
Sunburst520071968
Shelby520242015
Virgelle420241979
Circle420231969
Shawmut420241979
Beaverhead420241973
Ester Lake420242015
Wheat Basin420242017
Chuffey Spring420242018
Oswego320241978
Jordan320171968
Willow Creek 2320241983
Chinook320242015
Saco320242015
Wolf Creek320192015
Lindsay320242015
Threemile Wa320121999
Kalispell220241976
Harlem220211968
Redstone220231968

Northern Harrier Population Trend in Other States

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

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