Sportfishermen hate them. Aquafarmers see them as a threat to their livelihood. Property owners watch them threaten the beauty and value of their property.
Cormorants have insatiable appetites for fish. A single bird will consume over a pound of fish every day. The same bird might also kill or wound double that amount that they don’t eat.
I enjoy watching most predatory birds, like hawks, herons, eagles and ospreys. They are efficient and basically clean birds. They also tend not to congregate in large groups.
Cormorants are different. Their nests are often close together and many, often dozens can be seen hunting together. They can really wipe out a school of fish in a hurry. They can also cause hundreds of dollars of damage to an aquaculture pond in a day or two.
A problem farmers and homeowners face is that these birds are federally protected. They fall under the migratory bird protection act. This was a treaty between the United States and Canada that was signed a hundred years ago.
It was designed to protect birds that traveled between the two countries. We usually think of ducks and geese when someone mentions this treaty, but many other birds are included. The double-crested cormorant is probably the most controversial.
During the DDT era, cormorants weren’t much of a problem. Their reproduction was kept in check the same way it was for bald eagles. In 1972 this insecticide was outlawed in the US, and it wasn’t long before cormorant populations began to explode.
This came at a time when aquaculture in the southeastern states was in its early stages. Catfish farms present an easy food source for cormorants. Dense populations of fish quickly draw huge numbers of these gluttonous birds.
One of the reasons cormorants deplete fish populations so much is that they kill and eat so many smaller fish. This reduces total fish numbers drastically. Cormorants also kill and injure many larger fish that they don’t eat. Their serrated hooked beaks can inflict mortal wounds even if the fish escapes.
On aquaculture farms, fish are often fed by automatic feeders. When food hits the water, the fish come to the surface. That’s when cormorants are most deadly. Farmers can obtain permits to control these birds, but it’s still an arduous task. Sometimes farmers use dogs to harass the predators. That usually keeps cormorants from nesting close to the food source, but these birds are relentless.
Depleting wild and domestic fish sources is not the only problem cormorants cause. They eat copious quantities of fish; that’s true. They also produce a tremendous amount of waste. Much of that goes through their digestive systems. They vomit significant quantities of indigestible matter, too.
When bird populations, particularly nesting sites are dense, the ammonia from the excrement and vomit can be toxic to soils. Trees and other plants can die because of it. The residue is also unsightly. It smells terrible too. I realize every creature has a place in the ecosystem, but I see few redeeming qualities of the double-crested cormorant.
Ted Manzer teaches agriculture at Northeastern High School.