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

Western Gull Population Trend in California

All statesWetland birds

Western Gull in California has collapsed: down 84% on the route-weighted index since 1970.

-84%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 →
18Routes 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 →
56YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Western 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 →

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 →

Western Gull has collapsed in California: down 84% on the route-weighted index since 1970.

Western Gull Population Forecast in California

If the recent trend holds, Western Gull in California is projected to rise about 36% by 2029 — from 0.68 in 2024 to a central estimate of 0.92 (95% range 0.00–2.8). A 5-year backtest shows a typical error of ±428.2%, with 100% of held-out values landing inside the 95% band.

+36%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 →
0.92Projected 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 →
0.00–2.895% 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 →
±428.2%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, Western Gull in California is projected to rise about 36% by 2029 — from 0.68 in 2024 to a central estimate of 0.92 (95% range 0.00–2.8). A 5-year backtest shows a typical error of ±428.2%, with 100% of held-out values landing inside the 95% band.19682029
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 →
20251.00.002.9
20260.990.002.9
20270.960.002.9
20280.940.002.8
20290.920.002.8

Western Gull Survey Routes in California

Routes recording Western 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 →
Bodega Bay10120211972
Mark West5019901990
Harbor Lake 24120242014
S Catalina3620221988
Fairfax2220241972
Santa Cruz I2019881988
Poway1919801973
Laytonville1219911974
Colma1119721968
Harbor Lake919911975
Fish Rock620141969
Crescent Cty420221973
Morro Bay420191973
Honeydew320171968
Point Reyes320121975
San Ysidro320191973
Redwood N.P.219991996
Navarro119981974

Western Gull Population Trend in Other States

oregonwashington

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