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

Pigeon Guillemot Population Trend in California

All statesGeneralists

Pigeon Guillemot in California has collapsed: down 87% on the route-weighted index since 1975.

-87%Since 1975TrendPercent 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 →
7Routes 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 →
38YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Pigeon Guillemot 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 →

Pigeon Guillemot has collapsed in California: down 87% on the route-weighted index since 1975.

Pigeon Guillemot Population Forecast in California

If the recent trend holds, Pigeon Guillemot in California is projected to stay roughly flat through 2024, near 0.01 (95% range 0.00–0.07). A 5-year backtest shows a typical error of ±60.5%, 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 →
0.01Projected 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 →
0.00–0.0795% 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 →
±60.5%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, Pigeon Guillemot in California is projected to stay roughly flat through 2024, near 0.01 (95% range 0.00–0.07). A 5-year backtest shows a typical error of ±60.5%, with 100% of held-out values landing inside the 95% band.19732024
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 →
20200.010.000.07
20210.010.000.07
20220.010.000.07
20230.010.000.07
20240.010.000.07

Pigeon Guillemot Survey Routes in California

Routes recording Pigeon Guillemot 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 →
Laytonville419901983
Bodega Bay320141973
Navarro219781978
S Catalina120192019
Honeydew119831980
Fish Rock120081975
Morro Bay120181973

Pigeon Guillemot Population Trend in Other States

alaskaoregonwashington

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