BirdAnalyst
Species · BCR 10 · BBS 2026 Release · 1966–2025

Common Merganser In Northern Rockies

All regionsNorthern RockiesWaterfowl

Common Merganser in Northern Rockies has risen sharply: up 68% on the route-weighted index since 1970.

+68%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 →
121Routes 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 →
54YearsYears 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 →

Common Merganser has risen sharply in Northern Rockies: up 68% on the route-weighted index since 1970.

Common Merganser In Northern Rockies Population Forecast

If the recent trend holds, Common Merganser in Northern Rockies is projected to rise about 148% by 2030 — from 0.20 in 2025 to a central estimate of 0.50 (95% range 0.00–1.4). A 5-year backtest shows a typical error of ±72.3%, with 100% of held-out values landing inside the 95% band.

+148%Change 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 →
0.50Projected 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 →
0.00–1.495% 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 →
±72.3%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, Common Merganser in Northern Rockies is projected to rise about 148% by 2030 — from 0.20 in 2025 to a central estimate of 0.50 (95% range 0.00–1.4). A 5-year backtest shows a typical error of ±72.3%, with 100% of held-out values landing inside the 95% band.19682030
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 →
20260.510.001.4
20270.500.001.4
20280.500.001.4
20290.500.001.4
20300.500.001.4

Routes In Northern Rockies

Routes recording Common Merganser 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 →
CascadeIDAHO1051984
Hayden ValWYOMING301986
Ne EntranceWYOMING92021
MoranWYOMING92016
BeaverheadMONTANA81997
MammothWYOMING72018
Green RiverWYOMING71984
KalispellMONTANA62007
Fish CreekMONTANA62019
NowoodWYOMING62024
N Fork Cda RIDAHO52019
Libby DamMONTANA52024
Sullivan LkWASHINGTON51999
Cape HornIDAHO42018
Rochat DivdeIDAHO42023
Red RockMONTANA41989
East Glacier ParkMONTANA42025
HarmonyWYOMING42025
SeedskadeeWYOMING42016
GoldenIDAHO32008
CentervilleIDAHO32019
AugustaMONTANA31997
Swan LakeMONTANA32023
Hebgen LakeMONTANA32025
Spring LakeWASHINGTON32021

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