BirdAnalyst
Species · BCR 22 · BBS 2025 Release · 1966–2024

Northern Harrier In Eastern Tallgrass Prairie

All regionsEastern Tallgrass PrairieGeneralists

Northern Harrier in Eastern Tallgrass Prairie has collapsed: down 82% on the route-weighted index since 1968.

-82%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 →
131Routes 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 collapsed in Eastern Tallgrass Prairie: down 82% on the route-weighted index since 1968.

Northern Harrier In Eastern Tallgrass Prairie Population Forecast

If the recent trend holds, Northern Harrier in Eastern Tallgrass Prairie is projected to stay roughly flat through 2029, near 0.02 (95% range 0.00–0.10). A 5-year backtest shows a typical error of ±57.5%, with 100% 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 →
0.02Projected 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 →
0.00–0.1095% 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 →
±57.5%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 Eastern Tallgrass Prairie is projected to stay roughly flat through 2029, near 0.02 (95% range 0.00–0.10). A 5-year backtest shows a typical error of ±57.5%, 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 →
20250.030.000.10
20260.030.000.10
20270.020.000.10
20280.020.000.10
20290.020.000.10

Routes In Eastern Tallgrass Prairie

Routes recording Northern Harrier in Eastern Tallgrass Prairie.
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 →
Mill CreekILLINOIS32010
Grape CreekILLINOIS32007
Cedar ValleyIOWA31990
BloomvilleOHIO32001
HolcombILLINOIS22021
ComptonILLINOIS21972
StreatorILLINOIS22024
PontiacILLINOIS21987
ClarksdaleILLINOIS21995
Mascoutah LkILLINOIS21967
JamestownILLINOIS22023
WalesIOWA21999
LaplandKANSAS21982
Rock CreekKANSAS22002
LakevilleMINNESOTA22000
FrontenacMINNESOTA22017
TrentonMISSOURI22005
NorborneMISSOURI22012
CosmosOHIO21996
W CarrolltonOHIO22004
LondonOHIO22005
RaymondWISCONSIN21980
SheffieldILLINOIS12018
BudaILLINOIS12021
WayneILLINOIS11968

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