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

Osprey Population Trend in California

All statesGeneralists

Osprey in California has surged: up 117% on the route-weighted index since 1971.

+117%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 →
95Routes 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 Osprey 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 →

Osprey has surged in California: up 117% on the route-weighted index since 1971.

Osprey Population Forecast in California

If the recent trend holds, Osprey in California is projected to rise about 76% by 2029 — from 0.31 in 2024 to a central estimate of 0.55 (95% range 0.27–0.83). A 5-year backtest shows a typical error of ±254.4%, with 0% of held-out values landing inside the 95% band.

+76%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 →
0.55Projected 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 →
0.27–0.8395% 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 →
±254.4%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, Osprey in California is projected to rise about 76% by 2029 — from 0.31 in 2024 to a central estimate of 0.55 (95% range 0.27–0.83). A 5-year backtest shows a typical error of ±254.4%, with 0% 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 →
20250.520.240.80
20260.530.250.81
20270.540.260.82
20280.540.260.82
20290.550.270.83

Osprey Survey Routes in California

Routes recording Osprey 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 →
Iron Gate2620191988
Redwood N.P.1520101997
Bodega Bay1220181972
Horse Creek620191970
Hughson520241997
Oroville420242013
Copperopolis420241999
Whiskeytown420132002
Bass Lake320182002
Genesee320241991
Hackamore320032000
Chilcoot320092009
Nubieber220061988
Hullville220181981
Pennington220242008
Westville220171972
Morro Bay219731973
Point Reyes220221973
Shasta Lake220071974
Johnsville220152010
Lake Berryessa220242023
Arvin220152015
Redding219761976
Orleans220111978
Higgins Corn220112011

Osprey Population Trend in Other States

alabamaalaskaarizonaarkansascoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinaohiooregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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