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

Double-crested Cormorant Population Trend in Colorado

All statesWetland birds

Double-crested Cormorant in Colorado has surged: up 18× on the route-weighted index since 1989.

18×Since 1989TrendPercent 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 →
28Routes 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 →
38YearsYears 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 ColoradoNotable 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 Colorado: up 18× on the route-weighted index since 1989.

Double-crested Cormorant Population Forecast in Colorado

If the recent trend holds, Double-crested Cormorant in Colorado is projected to fall about 21% by 2030 — from 2.7 in 2025 to a central estimate of 2.1 (95% range 1.1–3.1). A 5-year backtest shows a typical error of ±36.6%, with 60% of held-out values landing inside the 95% band.

-21%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 →
2.1Projected 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 →
1.1–3.195% 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 →
±36.6%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 Colorado is projected to fall about 21% by 2030 — from 2.7 in 2025 to a central estimate of 2.1 (95% range 1.1–3.1). A 5-year backtest shows a typical error of ±36.6%, with 60% of held-out values landing inside the 95% band.19842030
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 →
20261.90.912.9
20272.00.963.0
20282.01.03.0
20292.11.13.1
20302.11.13.1

Double-crested Cormorant Survey Routes in Colorado

Routes recording Double-crested Cormorant in Colorado.
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 →
Guffey27220251997
Hudson1220251988
Arsenal720151991
Wildhorse L720242004
Julesburg720192002
Stillwater Pass720092001
Haswell620062006
Arsenal 2520252016
Last Chance519941991
Neegrande420181997
Animas 2320212016
Fort Morgan320212001
Doyleville220032003
Stoneham220142014
Harmony120082008
Kiowa120051995
Abarr120052005
Dolores119841984
Walden120251992
Cortez 2120092009
Tarryall120251991
Nunn120182001
Antonito119991996
Deadman Rd.120102010
De Beque120122012

Double-crested Cormorant Population Trend in Other States

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

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