BirdAnalyst
Species · California · BBS 2025 Release · 1966–2024

Great Horned Owl Population Trend in California

All statesGeneralists

Great Horned Owl in California has surged: up 193% on the route-weighted index since 1971.

+193%Since 1971TrendPercent 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 →
176Routes 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 →
55YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Great Horned Owl 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 →

long arc increasecomputed 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 →

Great Horned Owl has surged in California: up 193% on the route-weighted index since 1971.

Great Horned Owl Population Forecast in California

If the recent trend holds, Great Horned Owl in California is projected to stay roughly flat through 2029, near 0.43 (95% range 0.21–0.64). A 5-year backtest shows a typical error of ±36.2%, with 40% of held-out values landing inside the 95% band.

-10%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 →
0.43Projected 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 →
0.21–0.6495% 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 →
±36.2%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, Great Horned Owl in California is projected to stay roughly flat through 2029, near 0.43 (95% range 0.21–0.64). A 5-year backtest shows a typical error of ±36.2%, with 40% of held-out values landing inside the 95% band.19692029
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 →
20250.420.210.63
20260.420.210.63
20270.420.210.64
20280.420.210.64
20290.430.210.64

Great Horned Owl Survey Routes in California

Routes recording Great Horned Owl 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 →
Poloma1220231994
Pennington820141981
Tujunga819771971
Adelaida720241970
Joshua Tree619981970
Ono520091992
Point Reyes420221970
Anza419741974
Dorris420191979
Wawona420222005
Crescent Cty319721972
Bass Lake320051980
Foster Park319941970
Hollister319971974
Imperial Dam319881976
Lake Hemet319731970
Cuyamaca Pk320241977
Sanger320242012
Atwater320121986
Redding319791979
Junction Cty319941974
Macdoel320191983
Bridgeport319761976
Mark West320221974
Coyote320241972

Great Horned Owl Population Trend in Other States

alabamaalaskaarizonaarkansascoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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