BirdAnalyst
Species · BCR 23 · BBS 2025 Release · 1966–2024

Northern Harrier In Prairie Hardwood Transition

All regionsPrairie Hardwood TransitionGeneralists

Northern Harrier in Prairie Hardwood Transition has fallen sharply: down 64% on the route-weighted index since 1968.

-64%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 →
108Routes In RegionSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
58YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable SignalsNotable 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 fallen sharply in Prairie Hardwood Transition: down 64% on the route-weighted index since 1968.

Forecast

If the recent trend holds, Northern Harrier in Prairie Hardwood Transition is projected to stay roughly flat through 2029, near 0.20 (95% range 0.04–0.37). A 5-year backtest shows a typical error of ±150.4%, with 80% of held-out values landing inside the 95% band.

n/aChange 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 →
0.20Projected 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 →
0.04–0.3795% 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 →
±150.4%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 Prairie Hardwood Transition is projected to stay roughly flat through 2029, near 0.20 (95% range 0.04–0.37). A 5-year backtest shows a typical error of ±150.4%, with 80% 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 →
20250.210.040.37
20260.210.040.37
20270.200.040.37
20280.200.040.37
20290.200.040.37

Routes In Prairie Hardwood Transition

Routes recording Northern Harrier in Prairie Hardwood Transition.
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 →
NapoleonOHIO31996
No BradleyMICHIGAN21994
OwendaleMICHIGAN21992
S LyonsMICHIGAN21970
ChatfieldMINNESOTA21970
OsseoMINNESOTA22019
KnappMINNESOTA22019
Whitewater 2MINNESOTA22016
DresserWISCONSIN22022
LoraineWISCONSIN22018
MerrillWISCONSIN22023
Rolling PrWISCONSIN22017
MerideanWISCONSIN22009
Buena VistaWISCONSIN22022
AnnatonWISCONSIN22021
GuilfordILLINOIS11998
Lake GalenaILLINOIS12007
EllisINDIANA12015
FestinaIOWA12003
ScottvilleMICHIGAN11976
LawrenceMICHIGAN12008
New TroyMICHIGAN12005
Big RapidsMICHIGAN11981
NashvilleMICHIGAN12005
CoopersvilleMICHIGAN12003

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