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Species · California · BBS 2025 Release · 1966–2024

Glaucous-winged Gull Population Trend in California

All statesWetland birds

Glaucous-winged Gull in California has declined: down 26% on the route-weighted index since 1976.

-26%Since 1976TrendPercent 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 →
25YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Glaucous-winged Gull 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 →

No notable trend signals for Glaucous-winged Gull in California. See the full index history below.

Glaucous-winged Gull Population Forecast in California

If the recent trend holds, Glaucous-winged Gull in California is projected to stay roughly flat through 2024, near 0.02 (95% range 0.00–0.08). A 5-year backtest shows a typical error of ±285.4%, 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 →
0.02Projected 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 →
0.00–0.0895% 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 →
±285.4%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, Glaucous-winged Gull in California is projected to stay roughly flat through 2024, near 0.02 (95% range 0.00–0.08). A 5-year backtest shows a typical error of ±285.4%, 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 →
20200.020.000.09
20210.020.000.09
20220.020.000.09
20230.020.000.08
20240.020.000.08

Glaucous-winged Gull Survey Routes in California

Routes recording Glaucous-winged Gull 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 →
Navarro1019951990
Point Reyes619931992
Crescent Cty320011977
Bodega Bay120191975
Honeydew120161975
Fish Rock120001980
Fairfax119801973
Laytonville119911981

Glaucous-winged Gull Population Trend in Other States

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