BirdAnalyst
Species · BCR 12 · BBS 2025 Release · 1966–2024

Common Merganser In Boreal Hardwood Transition

All regionsBoreal Hardwood TransitionWaterfowl

Common Merganser in Boreal Hardwood Transition has surged: up 113% on the route-weighted index since 1973.

+113%Since 1973TrendPercent 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 →
63Routes 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 →
46YearsYears 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 surged in Boreal Hardwood Transition: up 113% on the route-weighted index since 1973.

Common Merganser In Boreal Hardwood Transition Population Forecast

If the recent trend holds, Common Merganser in Boreal Hardwood Transition is projected to rise about 72% by 2029 — from 0.05 in 2024 to a central estimate of 0.09 (95% range 0.00–0.19). A 5-year backtest shows a typical error of ±172.7%, with 100% of held-out values landing inside the 95% band.

+72%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 →
0.09Projected 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 →
0.00–0.1995% 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 →
±172.7%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, Common Merganser in Boreal Hardwood Transition is projected to rise about 72% by 2029 — from 0.05 in 2024 to a central estimate of 0.09 (95% range 0.00–0.19). A 5-year backtest shows a typical error of ±172.7%, with 100% of held-out values landing inside the 95% band.19672029
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 →
20250.090.000.18
20260.090.000.19
20270.090.000.19
20280.090.000.19
20290.090.000.19

Routes In Boreal Hardwood Transition

Routes recording Common Merganser in Boreal Hardwood Transition.
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 →
Red OakMICHIGAN72011
Wigwam BayMINNESOTA62018
Hiawatha NfMICHIGAN42013
CohassetMINNESOTA32021
BabbittMINNESOTA32022
McnaughtonWISCONSIN32013
BerglandMICHIGAN21990
Bear LakeMICHIGAN22011
OberlinMICHIGAN21994
Sand LakeMICHIGAN21996
GilmanWISCONSIN22004
CrandonWISCONSIN22018
MareniscoMICHIGAN11994
Ned LakeMICHIGAN12014
HermanMICHIGAN12022
Crystal FlsMICHIGAN12009
Gibbs CityMICHIGAN12013
Maple GroveMICHIGAN12017
IshpemingMICHIGAN12021
WilsonMICHIGAN12008
CunardMICHIGAN11997
MuskallongeMICHIGAN12013
GilchristMICHIGAN11997
Lake CityMICHIGAN11978
Skegemog PtMICHIGAN12023

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