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

Double-crested Cormorant In Boreal Hardwood Transition

All regionsBoreal Hardwood TransitionWetland birds

Double-crested Cormorant in Boreal Hardwood Transition has collapsed: down 78% on the route-weighted index since 1982.

-78%Since 1982TrendPercent 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 →
38YearsYears 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 →

Double-crested Cormorant has collapsed in Boreal Hardwood Transition: down 78% on the route-weighted index since 1982.

Double-crested Cormorant In Boreal Hardwood Transition Population Forecast

If the recent trend holds, Double-crested Cormorant in Boreal Hardwood Transition is projected to stay roughly flat through 2029, near 0.12 (95% range 0.00–1.0). A 5-year backtest shows a typical error of ±564.3%, 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 →
0.12Projected 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 →
0.00–1.095% 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 →
±564.3%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, Double-crested Cormorant in Boreal Hardwood Transition is projected to stay roughly flat through 2029, near 0.12 (95% range 0.00–1.0). A 5-year backtest shows a typical error of ±564.3%, with 100% of held-out values landing inside the 95% band.19782029
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 →
20250.140.001.1
20260.130.001.1
20270.130.001.1
20280.120.001.0
20290.120.001.0

Routes In Boreal Hardwood Transition

Routes recording Double-crested Cormorant 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 →
Hart LakeMINNESOTA381997
McgregorMINNESOTA241993
Pine RiverMINNESOTA221991
IsabellaMICHIGAN51988
CromwellMINNESOTA52001
BootjackMICHIGAN31998
Cass LakeMINNESOTA31990
Nett LakeMINNESOTA32016
Maple GroveMICHIGAN21992
IshpemingMICHIGAN21991
CathroMICHIGAN21995
Island LakeMINNESOTA21989
GreenbushMINNESOTA21996
PhillipsWISCONSIN21993
HermanMICHIGAN11993
MuskallongeMICHIGAN11997
PickfordMICHIGAN12000
Mille LacsMINNESOTA12024
Sherry LakeMINNESOTA11989
DebsMINNESOTA12010
LudeMINNESOTA11981
BrainerdMINNESOTA12004
NebishMINNESOTA11991
Tamarac NwrMINNESOTA12004
Iron RiverWISCONSIN12000

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