BirdAnalyst
Species · BCR 4 · BBS 2025 Release · 1966–2024

Bonaparte's Gull In BCR 4

All regionsBCR 4Wetland birds

Bonaparte's Gull in BCR 4 has fallen sharply: down 71% on the route-weighted index since 1984.

-71%Since 1984TrendPercent 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 →
33Routes 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 →
40YearsYears 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 →

Bonaparte's Gull has fallen sharply in BCR 4: down 71% on the route-weighted index since 1984.

Forecast

If the recent trend holds, Bonaparte's Gull in BCR 4 is projected to stay roughly flat through 2029, near 0.05 (95% range 0.00–0.38). A 5-year backtest shows a typical error of ±54.1%, with 100% of held-out values landing inside the 95% band.

n/aChange 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 →
0.05Projected 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 →
0.00–0.3895% 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 →
±54.1%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, Bonaparte's Gull in BCR 4 is projected to stay roughly flat through 2029, near 0.05 (95% range 0.00–0.38). A 5-year backtest shows a typical error of ±54.1%, with 100% of held-out values landing inside the 95% band.19822029
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 →
20250.080.000.42
20260.070.000.41
20270.060.000.40
20280.060.000.39
20290.050.000.38

Routes In BCR 4

Routes recording Bonaparte's Gull in BCR 4.
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 →
Bear CreekALASKA81988
PetersvilleALASKA51997
Nabesna RoadALASKA52016
SourdoughALASKA42001
Anvik RiverALASKA42014
KuskulanaALASKA41992
SlanaALASKA32013
MonahanALASKA32016
CottonwoodALASKA31990
ChistochinaALASKA21993
Pinoche Tral (Short)ALASKA21984
NorthwayALASKA12008
MaclarenALASKA11995
CantwellALASKA12016
ToklatALASKA11994
Skilak LakeALASKA11983
KalifonskyALASKA12015
WillowALASKA12022
Hatcher PassALASKA12013
Swan Lake RdALASKA12018
Lake LouiseALASKA11997
Nicholai SlALASKA12019
Seven LakesALASKA12018
KachemakALASKA12010
Burma RoadALASKA12024

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