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

California Gull Population Trend in Montana

All statesWetland birds

California Gull in Montana has fallen sharply: down 51% on the route-weighted index since 1970.

-51%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 →
43Routes 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 →
55YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable California Gull Trends in MontanaNotable 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 fallen sharply in Montana: down 51% on the route-weighted index since 1970.

California Gull Population Forecast in Montana

If the recent trend holds, California Gull in Montana is projected to rise about 424% by 2029 — from 0.11 in 2024 to a central estimate of 0.56 (95% range 0.00–4.8). A 5-year backtest shows a typical error of ±183.9%, with 100% of held-out values landing inside the 95% band.

+424%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 →
0.56Projected 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 →
0.00–4.895% 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 →
±183.9%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 Montana is projected to rise about 424% by 2029 — from 0.11 in 2024 to a central estimate of 0.56 (95% range 0.00–4.8). A 5-year backtest shows a typical error of ±183.9%, 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 →
20250.660.004.9
20260.630.004.8
20270.600.004.8
20280.580.004.8
20290.560.004.8

California Gull Survey Routes in Montana

Routes recording California Gull in Montana.
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 →
Pablo Res.2119981995
Great Falls1320231972
Jordan1120121968
Flatwillow 21020222017
Ingomar1019901990
Lima720041999
Beaverhead620051973
Ester Lake620242015
Saco620232015
Kalispell520032003
St Mary419911968
Flatwillow419991975
Glasgow320171979
Polson320101996
Boulder320172017
Oswego220211989
Glen220221988
Brusett220171987
Circle220181994
Two Dot220241985
Westby220162015
Whitlash220162012
Hay Lake120211988
Sunburst119981970
Virgelle120011984

California Gull Population Trend in Other States

alaskacaliforniacoloradoidahominnesotanevadanew-mexiconorth-dakotaoregonsouth-dakotautahwashingtonwyoming

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