BirdAnalyst
Species · BCR 32 · BBS 2025 Release · 1966–2024

Western Gull In Coastal California

All regionsCoastal CaliforniaWetland birds

Western Gull in Coastal California has fallen sharply: down 72% on the route-weighted index since 1970.

-72%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 →
11Routes In RegionSurvey 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 SignalsNotable 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 fallen sharply in Coastal California: down 72% on the route-weighted index since 1970.

Forecast

If the recent trend holds, Western Gull in Coastal California is projected to stay roughly flat through 2029, near 1.3 (95% range 0.00–3.5). A 5-year backtest shows a typical error of ±293.2%, with 100% of held-out values landing inside the 95% band.

-3%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 →
1.3Projected 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 →
0.00–3.595% 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 →
±293.2%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 →
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 →
20251.30.003.6
20261.30.003.6
20271.30.003.6
20281.30.003.5
20291.30.003.5

Routes In Coastal California

Routes recording Western Gull in Coastal 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 →
Mark WestCALIFORNIA501990
Harbor Lake 2CALIFORNIA412024
S CatalinaCALIFORNIA362022
FairfaxCALIFORNIA222024
Santa Cruz ICALIFORNIA201988
PowayCALIFORNIA191980
ColmaCALIFORNIA111972
Harbor LakeCALIFORNIA91991
Morro BayCALIFORNIA42019
San YsidroCALIFORNIA32019
Point ReyesCALIFORNIA32012

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