BirdAnalyst
Species · BCR 14 · BBS 2025 Release · 1966–2024

Double-crested Cormorant In Atlantic Northern Forest

All regionsAtlantic Northern ForestWetland birds

Double-crested Cormorant in Atlantic Northern Forest has surged: up 93% on the route-weighted index since 1971.

+93%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 →
51YearsYears 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 93% 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 rise about 27% by 2029 — from 0.13 in 2024 to a central estimate of 0.16 (95% range 0.00–0.51). A 5-year backtest shows a typical error of ±539.2%, with 100% of held-out values landing inside the 95% band.

+27%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 →
0.16Projected 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 →
0.00–0.5195% 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 →
±539.2%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 rise about 27% by 2029 — from 0.13 in 2024 to a central estimate of 0.16 (95% range 0.00–0.51). A 5-year backtest shows a typical error of ±539.2%, with 100% of held-out values landing inside the 95% band.19682029
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 →
20250.170.000.52
20260.170.000.51
20270.170.000.51
20280.170.000.51
20290.160.000.51

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
CornvilleMAINE142023
HancockMASSACHUSETTS122013
New HartfordCONNECTICUT111986
EastbrookMAINE71996
St DavidMAINE72005
PeterboroughNEW-HAMPSHIRE61975
CambridgeMAINE51982
RomeMAINE52005
New HartfordCONNECTICUT42003
HartfordMAINE42000
HancockMAINE42024
MedwayMAINE42014
ChesterfieldMASSACHUSETTS42013
MiddlesexVERMONT42011
FreedomMAINE31975
HarmonyMAINE32024
HermonMAINE31983
CastineMAINE32006
MilanNEW-HAMPSHIRE32023
GreenwoodMAINE22009
ManchesterMAINE21983
BrooksMAINE21985
MarlowNEW-HAMPSHIRE21992

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