Few attacks against wildlife are more irrational and bloody than the effort being made in Canada and the United States to kill off large numbers of double-crested cormorants while they are nesting. In Canada, Born Free USA is one of several animal protection and conservation organizations that are founding members of Cormorant Defenders International (CDI), which is dedicated to the protection of cormorants and other waterbirds that nest in colonies from culls. Our focus has been the lower Great Lakes, where both the federal and provincial governments have instigated culling of many thousands of birds while they are nesting.
The double-crested cormorant is a dark-colored, goose-sized bird related to pelicans. It originally was found from Alaska to Newfoundland, and from the northern Canadian prairies south into northern Mexico and the West Indies. It was, like a great many other species of native wildlife at the time of European colonization, heavily persecuted, particularly in the eastern part of North America, where it was eliminated from large areas, sometimes before records of its existence could be firmly established. Unfortunately, this left the impression among both the public and wildlife managers that cormorants previously were absent as a breeding species from parts of eastern and midwestern North America, including the entire Great Lakes region east of Lake of the Woods, on the Manitoba-Ontario border.
Early records of the birds breeding in the Great Lakes are scarce, but they do exist. Those records are conveniently ignored by wildlife managers who, until recently, persisted in regarding the cormorant as an “invasive” species that never nested in the Great Lakes, east of Lake of the Woods, prior to the 20th century.
During the 20th century, all agree, the species was nearly wiped out through much of its range by the effects of DDT (dichlorodiphenyltrichloroethane, an insecticide) following its development and wide use after World War II. Being at the top of the aquatic food chain, the species was, like the brown pelican, susceptible to the mass bioaccumulation of pesticides, leaving cormorants unable to lay eggs with shells of sufficient thickness to survive. But why it is important to understand that this was the second, not the first, elimination of the species is because if cormorants had been here in pre-Colonial times, obviously they co-evolved with native species of fish and other wildlife, without eliminating them. Since pre-Colonial fish stocks in the Great Lakes were robust, whatever diminished them in recent times, it was not cormorants, although cormorant numbers may be more enhanced by virtue of the presence of alien (non-native) fish species they eat, particularly Alewives and Round Gobies, both absent from the Great Lakes in pre-Colonial times.
The concerns about cormorants are many, but chief among them is the claim that they will “eat all the fish.” Fish are nearly the only thing cormorants will eat, and anglers fear that there are not enough fish for both them and the birds. It’s true that under some rather contrived circumstances — for example, near dams or in water impoundments or fish ponds — cormorants could make inroads on fish populations, but the very dependence cormorants have on fish is a guarantee, built on tens of millions of years of evolution, that they will not eliminate the fish.
Study after study over the past couple of centuries has shown that cormorants and other fish-eating birds (at various times loons, grebes, mergansers, kingfishers, ospreys, herons and other fish-eating species of bird have received the same persecution, for the same reason) rarely if ever have caused significant impacts on wild fish stocks of species desired by anglers and commercial fisheries. An extensive review of the existing scientific literature was done by the American Ornithologists Union, repudiating the U.S. Fish and Wildlife Service’s plans to kill off large numbers of cormorants.
The other major allegation made against cormorants is that they kill off vegetation, thereby ruining the environment. Cormorant excrement is high in nitrogen and other nutriments. Thus, adequately diluted, it is an excellent fertilizer. But concentrated under roosts or nesting colonies (cormorants nest in groups, either in trees or on the ground or on cliff ledges, often in the company of other “colonial” aquatic bird species such as herons and gulls) the guano kills off vegetation. It may coat leaves and block the process of photosynthesis. Cormorants will pull off twigs and branches for nesting materials, potentially further compromising the ability of trees and shrubs to survive.
But on the scale of things, loss of vegetation is a relatively limited, and certainly poses no threat. Ironically, many an island probably first had soil rich enough to support vegetation in the first place because of the earlier presence of nesting colonies of cormorants and other waterbirds. Such colonies are always changing, rarely if ever come close to being permanent and are, at any rate, all quite natural.
Wildlife management is politically, not scientifically, driven and the pressure from the sport and commercial fishing industry is relentless. No credit is given to the cormorant for being a natural predator, serving the function predators have always served within the ecological whole. While the kind of persecution that used to be directed against all predatory animals who dared to eat any prey desired by humans has slowly given way to an understanding that predator and prey relationships operate within basic ecological principles, cormorant “management” is mired in 19th century thinking, when animals were deemed “good” because they were pretty or ate things humans didn’t like, or they were deemed to be competitors with humans or just plain ugly, and categorized as “bad.”
There have been some successes — some culls halted or kept significantly below quotas thanks to the work, often voluntary, of Cormorant Defenders International. Academics have been very helpful, although some must assist the group anonymously as they are dependent on the very government agencies or commercial interests being challenged for funding for their work. But facts are on the side of the birds. Cormorants belong, and the bloodstained cruelty of culling is both logically and compassionately unjustified.