BirdAnalyst
Species · BCR 10 · BBS 2025 Release · 1966–2024

California Gull In Northern Rockies

All regionsNorthern RockiesWetland birds

California Gull in Northern Rockies has risen sharply: up 71% on the route-weighted index since 1970.

+71%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 →
62Routes 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 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 risen sharply in Northern Rockies: up 71% on the route-weighted index since 1970.

Forecast

If the recent trend holds, California Gull in Northern Rockies is projected to rise about 96% by 2029 — from 4.7 in 2024 to a central estimate of 9.3 (95% range 0.00–20). A 5-year backtest shows a typical error of ±601.6%, with 100% of held-out values landing inside the 95% band.

+96%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 →
9.3Projected 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 →
0.00–2095% 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 →
±601.6%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 Northern Rockies is projected to rise about 96% by 2029 — from 4.7 in 2024 to a central estimate of 9.3 (95% range 0.00–20). A 5-year backtest shows a typical error of ±601.6%, 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 →
20258.70.0020
20268.90.0020
20279.00.0020
20289.20.0020
20299.30.0020

Routes In Northern Rockies

Routes recording California Gull in Northern Rockies.
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 →
Neponset ResUTAH6862018
WoodruffUTAH6262024
CascadeIDAHO1201984
Saleratus CrUTAH1082018
Rock RiverWYOMING402022
EtheteWYOMING382024
FontenelleWYOMING342022
Hayden ValWYOMING251986
SeedskadeeWYOMING222014
Pablo Res.MONTANA211998
WilsonWYOMING101985
LimaMONTANA72004
HarmonyWYOMING72022
BeaverheadMONTANA62005
AlturasIDAHO51969
KalispellMONTANA52003
BridgeportOREGON51988
E. Bear LakeUTAH52012
CodyWYOMING52018
DuboisWYOMING51983
St MaryMONTANA41991
Sand DrawWYOMING42016
PolsonMONTANA32010
BoulderMONTANA32017
SpartaOREGON32001

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