快猫短视频

Around 50,000 double-crested cormorants are killed each year (Image: Shaunl/Getty)

They鈥檝e been called fish thieves, riverbank wreckers and alien invaders. But the slaughter of cormorants isn鈥檛 justified, says a conservation biologist

IN JULY 1998 I visited Naubinway, Michigan, for the first time. The town is one of the state鈥檚 few remaining commercial ports and fishing is the mainstay of its economy. But I wasn鈥檛 there for the fish. I was headed for a small island about a kilometre offshore, uninhabited by people but teeming with bird life in the summertime.

Herring gulls and double-crested cormorants begin nesting in this part of the Great Lakes in May, and by mid-June there are thousands of chicks. I went there with my University of Minnesota colleagues Francie Cuthbert and Dave Smith as part of a study of cormorant population dynamics. I didn鈥檛 know it then, but it was the beginning of a journey that would shape much of my life.

That year, low water levels had made the public jetty inaccessible, so we drove to the one used by commercial boats. Two fishermen watched us as we pulled up. Dave asked them if it was OK to use the jetty.

鈥淲hat do you want to do out there?鈥� the older man asked. Francie explained that we were conducting research on cormorants. The man nodded. 鈥淵eah, those birds are causing lots of trouble. Something needs to be done if we鈥檙e gonna fish here.鈥�

鈥淔ishing bad?鈥� Dave asked. The younger man snorted. 鈥淩eal bad. Won鈥檛 be no fish left soon. Gotta do something about those birds.鈥�

鈥淚s your research gonna help?鈥� the first man asked. Francie answered that it might help us understand the population better. The men looked sceptical, but gave their permission. As we put in, Francie told them we wouldn鈥檛 be on the island long. The younger man smiled. 鈥淭ake your time. Get as many cormorants as you can. We won鈥檛 tell.鈥�

It took only minutes to reach the island but it was as if the journey transported us to another world. As we approached, the cormorants took wing in a thunderous rush while the gulls swooped and shrieked overhead. The desolation of the island and the wildness of its inhabitants had an extraordinary effect on me. Though I had encountered cormorants many times before, seeing them in such numbers made me feel like I was experiencing them and their world for the first time. Since then I have visited many cormorant colonies, and come to realise that this bird is one of the most remarkable creatures I have ever encountered.

The same year I took that trip, two events occurred that would affect cormorants across North America for years. In March, the US Fish and Wildlife Service published a 鈥渄epredation order鈥� allowing fish farmers to shoot an unlimited number of cormorants without a permit. The order covered 13 states, 12 of them in the south-east, where catfish ponds are abundant and hundreds of thousands of cormorants overwinter. By the end of 2010, an estimated 300,000 cormorants had been killed under the order.

The second event was a vigilante-style slaying of double-crested cormorants at Little Galloo Island in Lake Ontario, which at the time supported some 8500 pairs, the largest known colony in the world. In July, biologists made a routine visit to the island and encountered a grisly scene: more than 800 dead, decaying cormorants and piles of shotgun shells.

Months later, nine men, many of whom were fishing guides, pleaded guilty to killing the birds. They were fined and sentenced to house arrest, but the incident was likened to the Boston Tea Party and the men attained local hero status.

This incident brought the cormorant 鈥減roblem鈥� into sharp focus for the Fish and Wildlife Service, culminating in 2003 in a second depredation order covering 24 states in the eastern US and allowing the killing of any cormorants deemed to be a threat to public resources, including fish, wildlife and land. By the end of 2011, this had resulted in the death of around 146,000 birds and the destruction of countless numbers of nests and eggs, mostly in the Great Lakes region. Thus began the modern American war on cormorants.

To begin to sense the injustice of this war, one must first understand just how extraordinary cormorants are. Consider their occurrence at Disko Bay in Greenland, where glaciers and icebergs abound. Most of the region鈥檚 animals are insulated from the cold by dense coats of fat, fur or waterproof feathers. All, that is, but for the great cormorant 鈥� the most widely distributed of the 40 or so species worldwide 鈥� which survives year-round in this frozen landscape despite lacking a substantial fat layer.

Not only does the cormorant survive, it thrives. Its fishing performance is the highest ever recorded for a marine predator. How do cormorants 鈥� which originated in the tropics 鈥� manage to live so successfully in the high Arctic? The answer lies partially in their exceptional plumage.

Cormorant feathers are unique amongst birds that hunt underwater, with an outer, wettable section and an inner, waterproof one. This confers two advantages: the outer section soaks up water, reducing the cormorant鈥檚 buoyancy, while the inner section retains an insulating layer of air against the skin. The result is a bird that can dive and pursue fish in a range of water depths and temperatures.

The eyes have it

This balance between buoyancy and insulation is just one of many unique adaptations. Another is their eyes. Not only are these often described as among the most beautiful of all birds鈥� eyes, they are also functionally remarkable. The unusually flexible lens changes shape extremely rapidly, while the muscles that regulate pupil size also act on the lens. These features presumably help cormorants find and catch fish underwater.

Yet how much the cormorant relies on vision isn鈥檛 clear. They hunt successfully in turbid waters and throughout the dark Arctic winter. So their hunting prowess must also depend on artful strategy, or some other adaptation as yet unknown.

Humans noticed this remarkable fishing skill a long time ago. For more than 2000 years, people in China have been taming cormorants and training them to bring back fish. This style of fishing is still practised in some parts of Asia.

Alas, the bird鈥檚 fishing talent is a double-edged sword, for it is this that brings it into direct conflict with humans. As a result, many cormorant species have been, and continue to be, persecuted in many parts of the world. In Europe, the great cormorant was almost hunted to extinction in the 19th century and is still widely culled. In Australia and New Zealand, many species have been intensely persecuted.

鈥淭heir fishing talent is a double-edged sword, as it brings them into conflict with humans鈥�

In North America, the persecution falls almost exclusively on the double-crested cormorant, the most common and widely distributed of six native species. In recent years, millions of US and Canadian dollars have been spent on reducing its numbers, based on a perception that it is the most significant bird predator on fish in North America.

The double-crested cormorant is certainly an efficient and adaptable predator, capable of exploiting a range of habitats from coastal bays to inland waterways. More than 60 families of fish have been documented in its diet. When birds are shot and their stomach contents examined, large numbers of intact fish are often observed, which only reinforces their reputation as voracious eaters.

Cormorants are also powerful agents of environmental change. Through their nesting and roosting habits 鈥� they are equally at home on the ground or in trees 鈥� they can denude a landscape of vegetation and cover it in guano. They can also defoliate and ultimately kill the trees they nest in. This destroys habitat for some groups of birds, though creates it for others.

Breeding colonies can build up to tens of thousands of birds filling every available space; occasionally, cormorants are observed nesting on top of dead cormorants. Guttural grunts, raucous calls, gargles, hisses and whines provide constant background noise and further amplify the impression of numerical greatness. Approaching such a colony from downwind, the reek of guano and rotting fish is detectable from quite a distance.

鈥淭he reek of guano and rotting fish is detectable from quite a distance鈥�

These attributes inspire fear, disgust, anger and hatred. Cormorants are often described as 鈥渋nvaders鈥� in regions in which they are actually native, and are often considered 鈥渙verabundant鈥�, even when they occur in relatively moderate numbers. For centuries, humans have gone to great lengths to destroy cormorants. Adults are usually shot and eggs are coated in oil, which asphyxiates the embryo but tricks the parents 鈥� which normally re-lay if their eggs are destroyed 鈥� into incubating eggs that will never hatch.

The depredation orders opened Pandora鈥檚 box, and those authorised to kill cormorants took extraordinary liberties. To grasp the magnitude of the persecution, consider that the number of cormorants legally destroyed in the US between 1998 and 2011 is in the same ball park as the total number of birds killed in the worst environmental disasters. The Exxon Valdez oil spill, for example, killed somewhere between 250,000 and 580,000 sea birds. The number of double-crested cormorants killed since 1998 is well over 500,000.

However, the extent to which cormorants actually harm human interests is unclear. Some prey species are commercially valuable, but the bulk of the cormorant鈥檚 diet consists of species not valued by humans. And despite its reputation for devouring fish, its daily food consumption relative to body mass is no greater than that for other fish-eating birds. To date, no study has demonstrated that cormorants pose a threat to the survival of healthy fish populations in natural systems.

To the agencies managing cormorants in the US, this is inconsequential. Scientific proof of impacts isn鈥檛 a required component of the regulations for management. Nor has there been any consideration of ethical dimensions.

The western front

To the extent that the agencies employ data, it is to argue that the number of birds destroyed is inconsequential relative to the total population. This is arguably true. An annual cull of 40,000 to 50,000 double-crested cormorants represents less than 5 per cent of the North American population. Clearly, the species isn鈥檛 in any imminent danger of being culled to extinction.

But is this the only criterion by which the efforts to suppress cormorant numbers should be judged? Half a million of anything is a large number. In addition, millions of dollars have been spent to sustain the effort, with little evidence that it does any good.

Nonetheless, the war on cormorants continues. Record numbers were killed in Michigan in 2012, and Minnesota expanded operations in 2013. The Great Lakes Restoration Initiative 鈥� a huge project to reverse decades of environmental degradation 鈥� has identified their destruction as an essential measure, on a par with cleaning up toxic substances and combating invasive species. Last August, both depredation orders were extended for another five years.

The war is also expanding westwards. In 2012, the Pacific Flyway Council, which coordinates the management of migratory birds in western North America, proposed managing cormorants to address conflicts over fish resources. And in 2014, the US Army Corps of Engineers proposed of cormorants on the Columbia river estuary on the Oregon-Washington border, to protect commercially valuable juvenile salmon and trout. If carried out, this would be the largest cull to date.

Yet there are also glimmers of hope. 快猫短视频s are increasingly questioning cormorant control in the scientific literature, in their comments on cormorant management plans, and in popular books. Encouraged by these moves, the US Center for Biological Diversity and other wildlife organisations to reconsider the routine use of lethal force to manage 鈥渘uisance鈥� wildlife including cormorants. More recently, Public Employees for Environmental Responsibility, a non-profit group that aims to improve management of public resources, has mounted a legal challenge to the renewal of the depredation orders.

In Canada, cormorants are culled to a much lesser extent and there is a greater willingness to use non-lethal methods. The , just outside downtown Toronto, is managed by deterring cormorants from nesting in trees or in sensitive areas. Efforts are also made to increase appreciation of the cormorant colony as a spectacular natural phenomenon in the heart of an urban wilderness.

I hold out hope for cormorants. As more information becomes available to dispel the myths and misconceptions about these birds, understanding, tolerance and even appreciation for them will increase.

Ultimately, the cormorant鈥檚 story reflects a culture still deeply prejudiced against creatures that exist outside the boundaries of human understanding and acceptance. To determine wildlife policy for these and other such creatures in the absence of scientific evidence is deeply flawed. I hope that by telling the cormorants鈥� side of the story, I can help to encourage a more nuanced and humane approach to this unique and fascinating family of birds.

See more animals that shouldn鈥檛 be called vermin: 鈥�Pest pardons: Five unjustly persecuted animals鈥�

This article appeared in print under the headline 鈥淎ngels of death鈥�