BirdAnalyst
Species · Idaho · BBS 2026 Release · 1966–2025

Northern Harrier Population Trend in Idaho

All statesBirds of prey

Northern Harrier in Idaho has declined: down 49% on the route-weighted index since 1970.

-49%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 →
47Routes 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 IdahoNotable 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 Idaho. See the full index history below.

Northern Harrier Population Forecast in Idaho

If the recent trend holds, Northern Harrier in Idaho is projected to stay roughly flat through 2030, near 0.66 (95% range 0.00–1.4). A 5-year backtest shows a typical error of ±20.5%, with 100% of held-out values landing inside the 95% band.

-3%Change by 2030TrendPercent 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 →
0.66Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–1.495% 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 →
±20.5%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 Idaho is projected to stay roughly flat through 2030, near 0.66 (95% range 0.00–1.4). A 5-year backtest shows a typical error of ±20.5%, with 100% of held-out values landing inside the 95% band.19682030
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 →
20260.690.001.5
20270.680.001.4
20280.670.001.4
20290.670.001.4
20300.660.001.4

Northern Harrier Survey Routes in Idaho

Routes recording Northern Harrier in Idaho.
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 →
Daniels Res520251988
Circular Bu420251985
Leadore420241979
Glenns Ferry419861969
Crane Creek420161988
Naples320241977
Twin Buttes320231990
Acequia320121979
Picabo320211988
Cabarton319941994
Mora320252019
Sawtooth Cty320141988
Pasadena Val320161987
Baker220241978
Dubois220251968
Centerville219821982
Craters220181980
Springfield220181969
Pocatello220181980
Sawtooth City 2220252015
Joel220051989
Iron Springs220241988
Silver City220131989
Cedar Hill220241990
Blackft Res120171987

Northern Harrier Population Trend in Other States

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

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.