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

Northern Harrier Population Trend in Washington

All statesBirds of prey

Northern Harrier in Washington has edged down: down 17% on the route-weighted index since 1970.

-17%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 →
66Routes 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 WashingtonNotable 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 Washington. See the full index history below.

Northern Harrier Population Forecast in Washington

If the recent trend holds, Northern Harrier in Washington is projected to rise about 33% by 2030 — from 0.31 in 2025 to a central estimate of 0.42 (95% range 0.07–0.77). A 5-year backtest shows a typical error of ±121.3%, with 80% of held-out values landing inside the 95% band.

+33%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 →
0.42Projected 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 →
0.07–0.7795% 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 →
±121.3%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 Washington is projected to rise about 33% by 2030 — from 0.31 in 2025 to a central estimate of 0.42 (95% range 0.07–0.77). A 5-year backtest shows a typical error of ±121.3%, with 80% 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 →
20260.420.070.77
20270.420.070.77
20280.420.070.77
20290.420.070.77
20300.420.070.77

Northern Harrier Survey Routes in Washington

Routes recording Northern Harrier in Washington.
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 →
Walla Walla819931993
Pomona619991998
Wilbur520211985
Ewan420191985
Potholes420191996
Arid Land Er319891988
Harrington320121973
Scootney Reservoir320252010
Keystone320251994
Odessa320251993
Mesa320081994
Moses Lake220211973
Mendota 2219941991
Wapato220211972
Bickleton220161984
Sulphur220191995
Curlew220122012
Richland220242006
Harwood219971993
Pomeroy220241998
Bay View220171999
Port Angeles120251984
Warm Beach120042004
Hanford Site119921989
Twisp120212021

Northern Harrier Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradodelawaregeorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-dakotatennesseetexasutahvermontvirginiawest-virginiawisconsinwyoming

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