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

Double-crested Cormorant Population Trend in Iowa

All statesWetland birds

Double-crested Cormorant in Iowa has collapsed: down 75% on the route-weighted index since 1992.

-75%Since 1992
11Routes In State
30Years

Notable Double-crested Cormorant Trends in Iowa

long arc declinecomputed index

Double-crested Cormorant has collapsed in Iowa: down 75% on the route-weighted index since 1992.

Double-crested Cormorant Population Forecast in Iowa

If the recent trend holds, Double-crested Cormorant in Iowa is projected to stay roughly flat through 2028, near 0.07 (95% range 0.00–0.50). A 5-year backtest shows a typical error of ±198.3%, with 100% of held-out values landing inside the 95% band.

n/aChange by 2028
0.07Projected 2028 index
0.00–0.5095% range
±198.3%Backtest error
19902028
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
20240.100.000.53
20250.090.000.52
20260.090.000.51
20270.080.000.51
20280.070.000.50

Double-crested Cormorant Survey Routes in Iowa

Routes recording Double-crested Cormorant in Iowa.
Wales1319911991
Titonka419931993
Maquoketa319941994
Scranton220011993
Gaza120081990
Melrose120231991
Bedford120132013
Bryant120191997
Williamsburg120112011
Sioux City120171991
Festina119971997

Double-crested Cormorant Population Trend in Other States

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

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