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

Northern Harrier Population Trend in Iowa

All statesGeneralists

Northern Harrier in Iowa has edged up: up 14% on the route-weighted index since 1982.

+14%Since 1982TrendPercent 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 →
19Routes 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 →
24YearsYears 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 IowaNotable 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 Iowa. See the full index history below.

Northern Harrier Population Forecast in Iowa

If the recent trend holds, Northern Harrier in Iowa is projected to stay roughly flat through 2027, near 0.07 (95% range 0.00–0.17). A 5-year backtest shows a typical error of ±79.3%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2027TrendPercent 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 →
0.07Projected 2027 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.1795% 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 →
±79.3%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 Iowa is projected to stay roughly flat through 2027, near 0.07 (95% range 0.00–0.17). A 5-year backtest shows a typical error of ±79.3%, with 100% of held-out values landing inside the 95% band.19682027
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 →
20230.070.000.17
20240.070.000.17
20250.070.000.17
20260.070.000.17
20270.070.000.17

Northern Harrier Survey Routes in Iowa

Routes recording Northern Harrier in Iowa.
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 →
Cedar Valley319901982
Wales219991999
Garner219901987
Mt Hamill119851985
Exline120042004
Melrose120052002
Bedford119991999
Bryant120061990
Brooklyn120102010
Red Rock119891989
Prairieburg120181968
Hudson120212021
Kanawha120182004
Washta119831983
Festina120031993
Davis Corner120221987
Gaza120092009
Rock Valley119881972
Tipton120082008

Northern Harrier Population Trend in Other States

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

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