BirdAnalyst
Species · BCR 16 · BBS 2025 Release · 1966–2024

California Gull In Southern Rockies / Colorado Plateau

All regionsSouthern Rockies / Colorado PlateauWetland birds

California Gull in Southern Rockies / Colorado Plateau has surged: up 15× on the route-weighted index since 1974.

15×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 →
26Routes 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 →
50YearsYears 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 increasecomputed 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 surged in Southern Rockies / Colorado Plateau: up 15× on the route-weighted index since 1974.

Forecast

If the recent trend holds, California Gull in Southern Rockies / Colorado Plateau is projected to fall about 22% by 2029 — from 9.2 in 2024 to a central estimate of 7.2 (95% range 2.2–12). A 5-year backtest shows a typical error of ±42.7%, with 60% of held-out values landing inside the 95% band.

-22%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 →
7.2Projected 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 →
2.2–1295% 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 →
±42.7%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 Southern Rockies / Colorado Plateau is projected to fall about 22% by 2029 — from 9.2 in 2024 to a central estimate of 7.2 (95% range 2.2–12). A 5-year backtest shows a typical error of ±42.7%, with 60% of held-out values landing inside the 95% band.19692029
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 →
20256.61.612
20266.71.812
20276.91.912
20287.02.112
20297.22.212

Routes In Southern Rockies / Colorado Plateau

Routes recording California Gull in Southern Rockies / Colorado Plateau.
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 →
GuffeyCOLORADO9822024
KamasUTAH1982024
TincupCOLORADO222011
WaldenCOLORADO92024
BeckUTAH51987
Beck 2UTAH51990
FerronUTAH52009
Lost LakeCOLORADO42010
HarmonyCOLORADO32018
DulceNEW-MEXICO32024
TarryallCOLORADO22023
Dixie NfUTAH21994
BufordWYOMING22001
Sybille CynWYOMING21999
YampaCOLORADO12010
Weston PassCOLORADO12000
ComoCOLORADO11998
Stillwater PassCOLORADO12006
BeaverUTAH11981
Navajo LakeUTAH12019
AnethUTAH12007
Uintah NfUTAH11993
M Warner ResUTAH11993
VernalUTAH12006
Lost Cr. ResUTAH12017

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