BirdAnalyst
Species · BCR 13 · BBS 2025 Release · 1966–2024

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 216% on the route-weighted index since 1990.

+216%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 →
22Routes 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 →
36YearsYears 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 216% on the route-weighted index since 1990.

Forecast

If the recent trend holds, Double-crested Cormorant in Lower Great Lakes / St. Lawrence Plain is projected to fall about 54% by 2029 — from 0.21 in 2024 to a central estimate of 0.10 (95% range 0.00–0.66). A 5-year backtest shows a typical error of ±91.8%, with 80% of held-out values landing inside the 95% band.

-54%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 →
0.10Projected 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 →
0.00–0.6695% 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 →
±91.8%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 Lower Great Lakes / St. Lawrence Plain is projected to fall about 54% by 2029 — from 0.21 in 2024 to a central estimate of 0.10 (95% range 0.00–0.66). A 5-year backtest shows a typical error of ±91.8%, with 80% of held-out values landing inside the 95% band.19882029
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 →
20250.130.000.69
20260.120.000.69
20270.110.000.68
20280.100.000.67
20290.100.000.66

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 →
MiddlefieldOHIO151996
St JohnsburgNEW-YORK91998
HamburgNEW-YORK82013
HighlandNEW-YORK72022
OgdensburgNEW-YORK62024
GhentNEW-YORK42004
CayugaNEW-YORK41990
MacdougallNEW-YORK42021
CrescentNEW-YORK32019
BranchportNEW-YORK12015
Cherry HillNEW-YORK12014
Cicero CtrNEW-YORK12010
SalemNEW-YORK12024
North EastonNEW-YORK12013
WillsboroNEW-YORK12019
PhiladelphiaNEW-YORK12024
PittsfieldOHIO12022
Herner CrnsOHIO12024
EspyvillePENNSYLVANIA12023
TeeplevillePENNSYLVANIA11992
ColchesterVERMONT12009
Grand IsleVERMONT12024

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