BirdAnalyst
Species · BCR 4 · BBS 2026 Release · 1966–2025

Red-breasted Merganser In BCR 4

All regionsBCR 4Waterfowl

Red-breasted Merganser in BCR 4 has surged: up 178% on the route-weighted index since 1991.

+178%Since 1991TrendPercent 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 →
16Routes 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 →
35YearsYears 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 →

Red-breasted Merganser has surged in BCR 4: up 178% on the route-weighted index since 1991.

Red-breasted Merganser In BCR 4 Population Forecast

If the recent trend holds, Red-breasted Merganser in BCR 4 is projected to stay roughly flat through 2030, near 0.86 (95% range 0.00–1.7). A 5-year backtest shows a typical error of ±823.8%, with 80% of held-out values landing inside the 95% band.

n/aChange by 2030TrendPercent 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 →
0.86Projected 2030 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–1.795% 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 →
±823.8%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, Red-breasted Merganser in BCR 4 is projected to stay roughly flat through 2030, near 0.86 (95% range 0.00–1.7). A 5-year backtest shows a typical error of ±823.8%, with 80% of held-out values landing inside the 95% band.19872030
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 →
20260.810.001.7
20270.820.001.7
20280.830.001.7
20290.850.001.7
20300.860.001.7

Routes In BCR 4

Routes recording Red-breasted Merganser 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 →
Anvik RiverALASKA112024
Unalakleet RiverALASKA52024
Kanuti CanynALASKA42024
KalifonskyALASKA32013
SlanaALASKA22013
MonahanALASKA21991
Nicholai SlALASKA21999
Seven LakesALASKA22019
Manley Ht SpALASKA22015
Porcupine R.ALASKA22000
Kanuti LakeALASKA22015
Paxson LakeALASKA21996
MaclarenALASKA12025
Kenny LakeALASKA11988
Anchor RiverALASKA12024
TatalinaALASKA12012

Source: USGS North American Breeding Bird Survey, retrieved 2026-08-14.