BUFFALO NY - In the Upper Niagara River, part of the ecology is facing a hard truth regarding the folly of introducing non-native species. The situation begins with the double crested cormorant, a native migratory water bird with a robust population in the river.
Their proliferation now is ironic given they were almost completely decimated in the 1970s. The pesticide DDT and human persecution were the main reasons for their decline.
"Since about the early 1970s, two things happened. We got rid of the toxins in the environment through regulations that banned DDT, as well as the species gained protection under the Migratory Bird Treaty," explains Tim DePriest, a New York DEC habitat biologist.
The cormorants didn't need any more help after that. Their numbers increased over the years. Skilled predators, they are perfectly adapted to their environment. Cormorants are actually related to pelicans.
"The thing that they have in common with pelicans is their foot structure. They have something called a Todydactyl foot structure which allows them to exceed at swimming underwater, using their feet as propulsion underwater," said DePriest.
So considering their predation skills, you wouldn't think the cormorant would need any help surviving, but in the river, they're getting just that from some invasive species.
"The zebra and quagga mussels that were introduced from Asia, the effect they had on the ecosystem was to, among other things, increase water clarity, and given that the double crested cormorant is an aquatic predator, having clear water makes their job a lot easier," said DePriest.
After the mussels, the round goby was introduced to Lake Erie in 1995. Cormorants found gobies to be great prey and easier to find in the clearer water.
"So clear water and the abundant round goby as an easy prey item made their living a lot easier, and their populations responded by increasing dramatically, exponentially," said DePriest.
But what's good for one species is not necessarily good for another.
Motor Island in the river is an important nesting ground for colonial nesting birds of all species, including great blue herons and egrets. The cormorant explosion is forcing other species off of the island.
They are also having a devastating effect on the island's vegetation. The waste from their excessive numbers is killing vegetation and affecting soil chemistry.
"Not only that but their nesting behavior is detrimental to these trees," said DePriest. "They actually strip the leaves and twigs and branches off the trees for making their nests."
The lesson for man involves awareness. Invasive species are here because of us, and thus, we must take responsibility for the future.
"Accidents of species introduction or even sometimes intentional species introductions have impacts beyond our control. If you're at all concerned about any of these factors, do everyone a favor and educate yourself, and pay attention," said DePriest.
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