BirdAnalyst
Species · Ohio · BBS 2026 Release · 1966–2025

Double-crested Cormorant Population Trend in Ohio

All statesWetland birds

Double-crested Cormorant in Ohio has surged: up 138% on the route-weighted index since 1997.

+138%Since 1997TrendPercent 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 →
15Routes In StateSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
24YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Double-crested Cormorant Trends in OhioNotable 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 Ohio: up 138% on the route-weighted index since 1997.

Double-crested Cormorant Population Forecast in Ohio

If the recent trend holds, Double-crested Cormorant in Ohio is projected to fall about 57% by 2030 — from 0.29 in 2025 to a central estimate of 0.13 (95% range 0.00–0.32). A 5-year backtest shows a typical error of ±73.1%, with 60% of held-out values landing inside the 95% band.

-57%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 →
0.00–0.3295% 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 →
±73.1%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 Ohio is projected to fall about 57% by 2030 — from 0.29 in 2025 to a central estimate of 0.13 (95% range 0.00–0.32). A 5-year backtest shows a typical error of ±73.1%, with 60% of held-out values landing inside the 95% band.19952030
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 →
20260.120.000.31
20270.120.000.31
20280.120.000.31
20290.130.000.32
20300.130.000.32

Double-crested Cormorant Survey Routes in Ohio

Routes recording Double-crested Cormorant in Ohio.
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 →
Middlefield1519961996
Vickery1220152015
Lockport620252025
Botkins319981998
Harveysburg 2220252025
Kunkle120022002
New Dover120182018
Lattasburg120252025
Pittsfield120222008
Limestone120221998
Ashley120161995
Baxter Ridge120252025
Norwalk120232023
Stonecreek120062006
Herner Crns120241997

Double-crested Cormorant Population Trend in Other States

alabamaalaskaarizonaarkansascaliforniacoloradoconnecticutdelawarefloridageorgiaidahoillinoisindianaiowakansaskentuckylouisianamainemarylandmassachusettsmichiganminnesotamississippimissourimontananebraskanevadanew-hampshirenew-jerseynew-mexiconew-yorknorth-carolinanorth-dakotaoklahomaoregonpennsylvaniarhode-islandsouth-carolinasouth-dakotatennesseetexasutahvermontvirginiawashingtonwest-virginiawisconsinwyoming

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