BirdAnalyst
Species · Illinois · BBS 2025 Release · 1966–2024

Double-crested Cormorant Population Trend in Illinois

All statesWetland birds

Double-crested Cormorant in Illinois has surged: up 721% on the route-weighted index since 1984.

+721%Since 1984
48Routes In State
37Years

Notable Double-crested Cormorant Trends in Illinois

long arc increasecomputed index

Double-crested Cormorant has surged in Illinois: up 721% on the route-weighted index since 1984.

Double-crested Cormorant Population Forecast in Illinois

If the recent trend holds, Double-crested Cormorant in Illinois is projected to rise about 353% by 2029 — from 0.12 in 2024 to a central estimate of 0.54 (95% range 0.05–1.0). A 5-year backtest shows a typical error of ±467.9%, with 40% of held-out values landing inside the 95% band.

+353%Change by 2029
0.54Projected 2029 index
0.05–1.095% range
±467.9%Backtest error
19742029
Projection of the recent trend (dashed) with 80/95% bands — a projection, not a prediction. Habitat, climate, and land use are not modeled.
YearProjected index95% low95% high
20250.510.021.0
20260.520.021.0
20270.530.031.0
20280.540.041.0
20290.540.051.0

Double-crested Cormorant Survey Routes in Illinois

Routes recording Double-crested Cormorant in Illinois.
Karnak2420132013
Nilwood2319951995
Barrington1020121990
Yorkville820192001
Dudleyville720212008
Sandusky720162016
Atkinson520192019
St Morgan520222009
Seneca420192009
Itasca320222004
Wayne320241990
Janesville320222019
Lake Summerset320132008
Flora319951995
Bartonville220222022
Monticello220212021
Belleview220072007
Keithsburg220052005
Delwood220241991
Royalton220022002
Shannon220222002
Guilford120182003
Geneseo120151993
Putnam120222018
Sheffield120092004

Double-crested Cormorant Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaohiooklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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