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

Swainson's Hawk Population Trend in California

All statesBirds of prey

Swainson's Hawk in California has surged: up 28× on the route-weighted index since 1974.

28×Since 1974TrendPercent 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 →
51Routes 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 →
52YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Swainson's Hawk Trends in CaliforniaNotable 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 Swainson's Hawk in California. See the full index history below.

Swainson's Hawk Population Forecast in California

If the recent trend holds, Swainson's Hawk in California is projected to stay roughly flat through 2030, near 0.83 (95% range 0.25–1.4). A 5-year backtest shows a typical error of ±50.4%, with 100% of held-out values landing inside the 95% band.

-1%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 →
0.83Projected 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 →
0.25–1.495% 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 →
±50.4%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, Swainson's Hawk in California is projected to stay roughly flat through 2030, near 0.83 (95% range 0.25–1.4). A 5-year backtest shows a typical error of ±50.4%, with 100% of held-out values landing inside the 95% band.19722030
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 →
20260.760.181.3
20270.780.201.4
20280.790.211.4
20290.810.231.4
20300.830.251.4

Swainson's Hawk Survey Routes in California

Routes recording Swainson's Hawk in California.
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 →
Collegeville 24220232007
Ora Loma3120251981
Athlone2420071972
Westley1520251974
Atwater1420121974
Buena Vista820192017
Zamora720251977
Tracy 2620242010
Hughson520251994
Sattley420242024
Staten Is.420251994
Likely320251976
Nubieber220072007
Collegeville220041980
Madeline220252012
Dorris220191992
Tranquillity220241981
Parker Dam219751975
Tracy220092002
Glamis219741974
Ingalls220251991
Iron Gate120062006
Carrizo Pln120222009
Pennington120251972
Riovista120222005

Swainson's Hawk Population Trend in Other States

alaskaarizonaarkansascoloradoidahoillinoisiowakansaslouisianaminnesotamissourimontananebraskanevadanew-mexiconorth-dakotaoklahomaoregonsouth-dakotatexasutahwashingtonwisconsinwyoming

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