BirdAnalyst
Species · South Dakota · BBS 2025 Release · 1966–2024

Northern Harrier Population Trend in South Dakota

All statesGeneralists

Northern Harrier in South Dakota has declined: down 49% on the route-weighted index since 1969.

-49%Since 1969TrendPercent 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 →
50Routes 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 South DakotaNotable 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 South Dakota. See the full index history below.

Northern Harrier Population Forecast in South Dakota

If the recent trend holds, Northern Harrier in South Dakota is projected to fall about 47% by 2029 — from 0.86 in 2024 to a central estimate of 0.46 (95% range 0.00–1.2). A 5-year backtest shows a typical error of ±20.7%, with 100% of held-out values landing inside the 95% band.

-47%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 →
0.46Projected 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 →
0.00–1.295% 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 →
±20.7%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 South Dakota is projected to fall about 47% by 2029 — from 0.86 in 2024 to a central estimate of 0.46 (95% range 0.00–1.2). A 5-year backtest shows a typical error of ±20.7%, with 100% of held-out values landing inside the 95% band.19672029
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 →
20250.500.001.3
20260.490.001.3
20270.480.001.2
20280.470.001.2
20290.460.001.2

Northern Harrier Survey Routes in South Dakota

Routes recording Northern Harrier in South Dakota.
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 →
Conde519841967
Harding420191968
Reva420241979
Lodgepole420231995
Raymond320211967
Lane319991970
Britton320221967
Fort Pierre320241968
Maurine320241968
Chamberlain220101967
Volga220231967
Ft Thompson220071967
Gettysburg220191969
Promise220001971
Cedar Pass220211968
Gorman220091979
Hayes220241991
S. Pioneer220241994
Lennox120151968
Tripp120101967
Howard120211972
White Lake120111967
Geddes119941967
Winner120051968
Rosebud120101967

Northern Harrier Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradodelawaregeorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandtennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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