Named for head feathers appearing during breeding season, Double-crested Cormorants were adversely affected after WWII when the use of DDT was permissible as a pesticide. DDT, when broken down to DDE, causes egg shell thinning in birds at the end of the food chain so Osprey, Bald Eagles, and Cormorants had difficulty producing offspring because when they incubated their eggs, the shells were not strong enough to support the weight of an adult bird. Today, this species and others affected by DDT have rebounded from pre-1970 lows, and in areas of aquaculture where catfish and baitfish are raised in ponds and in sport fishing areas in the upper Midwest, cormorants are considered villains, congregating in these areas during winter months. In Shakespeare’s plays he uses the word ‘cormorant’ to mean villainous. Interestingly, both U.S. pelican species eat more fish per day than cormorants do, but because of pelican’s beauty, or possible because of white vs. black plumage, cormorants are considered foes.
In the northeast, cormorants have rebounded so much that people petitioned the U.S. Fish and Wildlife Service to open hunting seasons to reduce cormorant numbers where nesting cormorants’ guano has begun to kill trees at nesting sites and in areas where they were blamed for the drop in bluefish numbers. Cormorants focus on the smaller schooling “trash fish” and eat about one pound per day. In 24 states, aquaculture producers may now shoot cormorants feeding on private ponds, or they can call on government officials to shoot birds on nearby roosts and/or oil cormorant eggs. As a result, about 40,000 cormorants are killed each year or about 2 percent of North America’s population in spite of an outcry by the National Audubon Association and animal rights groups.
In Colorado, Double-crested Cormorants nest in small colonies, like the ones at the west end of Pueblo Reservoir, and they are still considered uncommon on the Chico and in neighboring areas. This is a single Double-crested Cormorant on Chico Basin Ranch’s Upper Twin Pond. It is a young bird who was perched on a wooden post drying it feathers. Because of the nature of cormorant feathers, they have fewer oils than waterfowl feathers, so they must air-dry their feathers periodically or they will become waterlogged and sink.
As one Minnesota wildlife biologist summed up the situation in areas where cormorants are abundant…“at the heart of the issue is a nearly zero tolerance for cormorants.”