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

Red-breasted Merganser In BCR 4

All regionsBCR 4Waterfowl

Red-breasted Merganser in BCR 4 has surged: up 382% on the route-weighted index since 1991.

+382%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 →
34YearsYears 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 382% 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 rise about 66% by 2029 — from 0.58 in 2024 to a central estimate of 0.97 (95% range 0.15–1.8). A 5-year backtest shows a typical error of ±49.7%, with 100% of held-out values landing inside the 95% band.

+66%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 →
0.97Projected 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 →
0.15–1.895% 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 →
±49.7%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, Red-breasted Merganser in BCR 4 is projected to rise about 66% by 2029 — from 0.58 in 2024 to a central estimate of 0.97 (95% range 0.15–1.8). A 5-year backtest shows a typical error of ±49.7%, with 100% of held-out values landing inside the 95% band.19872029
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 →
20250.900.081.7
20260.920.101.7
20270.930.121.8
20280.950.131.8
20290.970.151.8

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
MaclarenALASKA31987
KalifonskyALASKA32013
SlanaALASKA22013
MonahanALASKA21991
Nicholai SlALASKA21999
Seven LakesALASKA22019
Manley Ht SpALASKA22015
Porcupine R.ALASKA22000
Kanuti LakeALASKA22015
Paxson LakeALASKA21996
Kenny LakeALASKA11988
Anchor RiverALASKA12024
TatalinaALASKA12012

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