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Species · BCR 14 · BBS 2026 Release · 1966–2025

Double-crested Cormorant In Atlantic Northern Forest

All regionsAtlantic Northern ForestWetland birds

Double-crested Cormorant in Atlantic Northern Forest has surged: up 101% on the route-weighted index since 1971.

+101%Since 1971TrendPercent 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 →
50Routes 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 →
52YearsYears 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 →

Double-crested Cormorant has surged in Atlantic Northern Forest: up 101% on the route-weighted index since 1971.

Double-crested Cormorant In Atlantic Northern Forest Population Forecast

If the recent trend holds, Double-crested Cormorant in Atlantic Northern Forest is projected to stay roughly flat through 2030, near 0.15 (95% range 0.00–0.49). A 5-year backtest shows a typical error of ±521.8%, with 100% 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 →
0.15Projected 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 →
0.00–0.4995% 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 →
±521.8%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, Double-crested Cormorant in Atlantic Northern Forest is projected to stay roughly flat through 2030, near 0.15 (95% range 0.00–0.49). A 5-year backtest shows a typical error of ±521.8%, 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 →
20260.160.000.50
20270.150.000.50
20280.150.000.50
20290.150.000.49
20300.150.000.49

Routes In Atlantic Northern Forest

Routes recording Double-crested Cormorant in Atlantic Northern Forest.
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 →
DebloisMAINE582007
JeffersonMAINE212007
HancockMASSACHUSETTS122013
New HartfordCONNECTICUT111986
EastbrookMAINE71996
St DavidMAINE72005
PeterboroughNEW-HAMPSHIRE61975
CambridgeMAINE51982
RomeMAINE52005
New HartfordCONNECTICUT42003
HartfordMAINE42000
MedwayMAINE42014
ChesterfieldMASSACHUSETTS42013
MiddlesexVERMONT42011
FreedomMAINE31975
HarmonyMAINE32024
HermonMAINE31983
CastineMAINE32006
MilanNEW-HAMPSHIRE32023
GreenwoodMAINE22009
ManchesterMAINE21983
BrooksMAINE21985
MarlowNEW-HAMPSHIRE21992
Post MillsVERMONT22007
NewcastleMAINE12008

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