BirdAnalyst
Species · BCR 32 · BBS 2025 Release · 1966–2024

Great Horned Owl In Coastal California

All regionsCoastal CaliforniaGeneralists

Great Horned Owl in Coastal California has surged: up 158% on the route-weighted index since 1972.

+158%Since 1972TrendPercent 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 →
95Routes 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 →
54YearsYears 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 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 Coastal California: up 158% on the route-weighted index since 1972.

Forecast

If the recent trend holds, Great Horned Owl in Coastal California is projected to stay roughly flat through 2029, near 0.73 (95% range 0.38–1.1). A 5-year backtest shows a typical error of ±40.4%, 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 →
0.73Projected 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 →
0.38–1.195% 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 →
±40.4%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, Great Horned Owl in Coastal California is projected to stay roughly flat through 2029, near 0.73 (95% range 0.38–1.1). A 5-year backtest shows a typical error of ±40.4%, with 40% of held-out values landing inside the 95% band.19702029
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 →
20250.710.361.1
20260.720.371.1
20270.720.371.1
20280.730.371.1
20290.730.381.1

Routes In Coastal California

Routes recording Great Horned Owl in Coastal 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 →
PolomaCALIFORNIA122023
PenningtonCALIFORNIA82014
TujungaCALIFORNIA81977
AdelaidaCALIFORNIA72024
OnoCALIFORNIA52009
Point ReyesCALIFORNIA42022
AnzaCALIFORNIA41974
Foster ParkCALIFORNIA31994
HollisterCALIFORNIA31997
Lake HemetCALIFORNIA31973
Cuyamaca PkCALIFORNIA32024
SangerCALIFORNIA32024
AtwaterCALIFORNIA32012
ReddingCALIFORNIA31979
Mark WestCALIFORNIA32022
CoyoteCALIFORNIA32024
Lake Hemet 2CALIFORNIA32016
Cleveland NfCALIFORNIA32016
Tres Pinos 2CALIFORNIA32009
ColmaCALIFORNIA21972
Santa YnezCALIFORNIA22003
Mt PinosCALIFORNIA21990
CoalingaCALIFORNIA22014
FolsomCALIFORNIA22023
Mesa GrandeCALIFORNIA22024

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