The Thousand Islands and the Plight of the Double-Crested Cormorants

The Thousand Islands is a lovely spot for a vacation or a day trip. There is lots of history, culture and natural beauty. The natural beauty of the islands is in contrast with the industrial might of the many transport ships traveling along the St. Lawrence Seaway. Home to many species, summer inhabitants of the Seaway include Osprey and Seagulls of all types.

This past summer, while on a boat trip in the Islands, I was introduced to Gull Island, a bird watchers’ paradise. Despite the name, Seagulls were not the main attraction of this tiny rock outcrop in the midst of the St. Lawrence River. Rather every available surface seemed to be covered with loud, socially active, nesting Double-Crested Cormorants.

Double-Crested Cormorants are a very interesting bird. Genetically related to a pelican, they resemble a loon while swimming. Both male and female Double-Crested Cormorants are all black birds, rather large in size, but lanky rather than stout at about thirty-three inches. Their long neck is a distinguishing feature, as is its bright, orange-yellow bill and face, made more stunning by the black surround. This bill has a hooked tip, very like a pronounced overbite, no doubt helpful in the pursuit of fish. The “Double-Crested” refers to two plumes or tufts of feathers that develop on either side of its head (about where ears would be) during the breeding season. The final, and in my mind most intriguing physical feature of the Double-Crested Cormorant is its sparkling, crystal-like blue eyes. Their eyes are very special as they have evolved to allow aerial and underwater vision. Underwater vision is particularly key for this species, as the birds diet consists of fish and mollusks.

As you would expect with an aquatic bird, swimming is a big part of the Cormorant’s life. Despite the fact that its name translated from Latin means “Sea Crow,” the Double-Crested Cormorant prefers fresh water to salt. If you see a Cormorant swimming, it is often alone or with a few fellow Cormorants. They bob in the water like a duck or a loon and then suddenly they dive with a great burst of speed and a splash. Because their pursuit of fish can be arduous, they are able to remain under the water for longer periods than ducks or geese. They also swim long distances and often pop up a yard or so away from their dive spot. Unlike a penguin, the Cormorant swims with its wings at its sides. Once the Cormorant returns to dry land, it is a very common site to see it standing with wings outstretched, the best method of drying its feathers in the sun.

Cormorants are colonizing birds, meaning they choose to nest in large groups. They are happy building nests either in trees or on the ground, however the whole colony will build consistently, so you will never find a colony where some nests are in trees with others on the ground. Each mating pair have one brood a year, of three or four eggs on average. The young Cormorants who grow up in ground colonies will get out of their nests after three or four weeks and wander the community, however they will still return to their nests to be fed. As they develop, the juvenile Cormorants take on a light gray or brownish color until their mature feathers grow in.

There is some controversy regarding the presence of Cormorants in the Great Lakes and Thousand Islands regions. Once a common resident of the Great Lakes Region, their populations were greatly diminished by a combination mandated population control and pollution in the 1940s-1960s. The elimination of DDT and other pesticides allowed their populations to grown throughout the 70’s and 80’s. Following this slow beginning, the population has been steadily increasing and they now thrive throughout the Great Lakes region. However, as living memory doesn’t reach beyond the time of DDT and its effects on the environment, many people look on the Double-Crested Cormorant as an invasive species.

The Cormorants’ large populations throughout the region has caused them to attract the attention of the fisherman, who feel the presence of so many Cormorants is negatively affecting their fishing. There are even some shocking reports of unlicensed killing of whole Cormorant colonies in an effort to protect fish populations in the region. The worst report I came across occurred in 1998 outside of Watertown, New York. 800 birds were killed in the name of recreational fishing. I am sad to say this is not an isolated incident. The decline of the Smallmouth Bass population specifically has been blamed on the increased populations of Double-Crested Cormorants, however the fisheries believe that a number of contributing factors, of which the Cormorant population is only one of many, has led to this population decline. Extensive studies of the Cormorant diet in the Great Lakes and Thousand Islands regions found this concern to be unfounded (study conducted in late 1990s). While a Cormorant’s diet does consist of a variety of sport fish, both Northern Pike and Smallmouth Bass comprised of only 3% of the fish they consumed. The same study found that smaller fish (pumpkinseed, yellow perch and rock bass) made up the majority of the Double-Crested Cormorant’s diet, about 83%. The same study found some differences in the diets of the birds residing in the St. Lawrence verses those birds that colonize in Lake Ontario, however these variances still did not effect the Smallmouth Bass populations. I also feel the need to point out that the Cormorants also do their bit for the Great Lakes/Thousand Islands ecosystems. They eat indiscriminately, meaning that their presence helps battle invasive species of fish and mollusks, such as the alewife and zebra mussel.

While they are innocent of the charges against them with regard to fish populations, the Cormorants are guilty of another crime which some of the locals think is just as bad. Their settlement on an island seems to spell impending doom for all vegetation and trees that live there. This phenomenon could definitely be seen from the state of Gull Island. This is directly related to the Cormorants’ excrement which is very rich with ammonia. The effect is worsened by the fact that the Cormorant lives in colonies, meaning that small areas receive a concentration of the droppings and they are repeat visitors, returning the same nesting location year after year, which gives the vegetation little time to recover.

In the discussion of these Cormorant controversies I do not mean to imply that people are totally wrong or that the Cormorants are completely victimized. I think one look at Gull Island can show that the Cormorant population is thriving in this region, which can have many negative effects on both the vegetation and habitats of other bird species. Rather, I think it is best left up to the New York Department of Environmental Conservation and other similar departments on both sides of the lakes to monitor and manage. The Cormorant population is being monitored and controlled in New York, which include nest destruction and nesting deterrents. The idea that wholesale slaughter of a bird population won’t have negative effects on the whole region demonstrates a lack of understanding I thought far behind us. Did we learn nothing from the Dodo? Individuals should never take matters into their own hands. Ecosystems are very delicate webs and the slightest changes can have catastrophic effects.

Sources

http://tilife.org/BackIssues/Archive/tabid/393/articleType/ArticleView/articleId/2101/The-Devils-Bird-in-the-St-Lawrence-River.aspx

http://www.glfc.org/pubs/lake_committees/ontario/cormorant.pdf

https://www.dec.ny.gov/animals/28442.html

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