BirdAnalyst
Species · BCR 15 · BBS 2025 Release · 1966–2024

California Gull In Sierra Nevada

All regionsSierra NevadaWetland birds

California Gull in Sierra Nevada has collapsed: down 98% on the route-weighted index since 1974.

-98%Since 1974TrendPercent 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 →
10Routes 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 →
39YearsYears 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 →

California Gull has collapsed in Sierra Nevada: down 98% on the route-weighted index since 1974.

California Gull In Sierra Nevada Population Forecast

If the recent trend holds, California Gull in Sierra Nevada is projected to stay roughly flat through 2022, near 1.1 (95% range 0.00–3.8). A 5-year backtest shows a typical error of ±3795.9%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2022TrendPercent 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 →
1.1Projected 2022 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–3.895% 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 →
±3795.9%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, California Gull in Sierra Nevada is projected to stay roughly flat through 2022, near 1.1 (95% range 0.00–3.8). A 5-year backtest shows a typical error of ±3795.9%, with 100% of held-out values landing inside the 95% band.19722022
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 →
20181.10.003.8
20191.10.003.8
20201.10.003.8
20211.10.003.8
20221.10.003.8

Routes In Sierra Nevada

Routes recording California Gull in Sierra Nevada.
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 →
GoumazCALIFORNIA802004
Tuolumne GroveCALIFORNIA151979
WoodfordsCALIFORNIA31983
LakeshoreCALIFORNIA31992
Eagle LakeCALIFORNIA12014
DardanelleCALIFORNIA12015
Bass LakeCALIFORNIA11976
SattleyCALIFORNIA12017
GeneseeCALIFORNIA12013
CrestviewCALIFORNIA12004

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