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Species · California · BBS 2025 Release · 1966–2024

Pelagic Cormorant Population Trend in California

All statesWetland birds

Pelagic Cormorant in California has fallen sharply: down 74% on the route-weighted index since 1970.

-74%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 →
8Routes 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 →
51YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Pelagic Cormorant 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 declinecomputed 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 →

Pelagic Cormorant has fallen sharply in California: down 74% on the route-weighted index since 1970.

Pelagic Cormorant Population Forecast in California

If the recent trend holds, Pelagic Cormorant in California is projected to stay roughly flat through 2024, near 0.00 (95% range 0.00–0.58). A 5-year backtest shows a typical error of ±94.5%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2024TrendPercent 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 →
0.00Projected 2024 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.5895% 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 →
±94.5%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, Pelagic Cormorant in California is projected to stay roughly flat through 2024, near 0.00 (95% range 0.00–0.58). A 5-year backtest shows a typical error of ±94.5%, with 100% of held-out values landing inside the 95% band.19682024
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 →
20200.010.000.59
20210.000.000.58
20220.000.000.58
20230.000.000.58
20240.000.000.58

Pelagic Cormorant Survey Routes in California

Routes recording Pelagic Cormorant 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 →
Bodega Bay420191972
Laytonville419911981
Navarro319851978
Honeydew220161968
Fish Rock220141973
Morro Bay220121978
Harbor Lake119821980
Fairfax120042004

Pelagic Cormorant Population Trend in Other States

alaskaoregonwashington

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