BirdAnalyst
Species · BCR 13 · BBS 2026 Release · 1966–2025

Double-crested Cormorant In Lower Great Lakes / St. Lawrence Plain

All regionsLower Great Lakes / St. Lawrence PlainWetland birds

Double-crested Cormorant in Lower Great Lakes / St. Lawrence Plain has surged: up 243% on the route-weighted index since 1990.

+243%Since 1990TrendPercent 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 →
23Routes 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 →
37YearsYears 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 Lower Great Lakes / St. Lawrence Plain: up 243% on the route-weighted index since 1990.

Double-crested Cormorant In Lower Great Lakes / St. Lawrence Plain Population Forecast

If the recent trend holds, Double-crested Cormorant in Lower Great Lakes / St. Lawrence Plain is projected to fall about 71% by 2030 — from 0.43 in 2025 to a central estimate of 0.13 (95% range 0.00–0.69). A 5-year backtest shows a typical error of ±93.6%, with 80% of held-out values landing inside the 95% band.

-71%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 →
0.13Projected 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 →
0.00–0.6995% 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 →
±93.6%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 Lower Great Lakes / St. Lawrence Plain is projected to fall about 71% by 2030 — from 0.43 in 2025 to a central estimate of 0.13 (95% range 0.00–0.69). A 5-year backtest shows a typical error of ±93.6%, with 80% of held-out values landing inside the 95% band.19882030
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 →
20260.150.000.72
20270.150.000.71
20280.140.000.70
20290.130.000.70
20300.130.000.69

Routes In Lower Great Lakes / St. Lawrence Plain

Routes recording Double-crested Cormorant in Lower Great Lakes / St. Lawrence Plain.
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 →
OgdensburgNEW-YORK172025
MiddlefieldOHIO151996
St JohnsburgNEW-YORK91998
HamburgNEW-YORK82013
HighlandNEW-YORK72022
GhentNEW-YORK42004
CayugaNEW-YORK41990
MacdougallNEW-YORK42021
CrescentNEW-YORK32019
BranchportNEW-YORK12015
Cherry HillNEW-YORK12014
Cicero CtrNEW-YORK12010
SalemNEW-YORK12024
North EastonNEW-YORK12013
WillsboroNEW-YORK12019
PhiladelphiaNEW-YORK12025
PittsfieldOHIO12022
Herner CrnsOHIO12024
LattasburgOHIO12025
EspyvillePENNSYLVANIA12023
TeeplevillePENNSYLVANIA11992
ColchesterVERMONT12009
Grand IsleVERMONT12025

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