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Loons on the Move

October 26, 2009
Common Loon

Some now call it the great loon die-off of 1983 when nearly 10,000 common loons washed up on the shores of the northern Gulf of Mexico from Florida to Texas. Emaciated, anemic, full of parasites, and loaded with toxic mercury from a fish diet, they did not have enough strength or coordination to survive. Although more than 1,000 miles away, biologists in the Northeast were deeply concerned.

“We suspected that some Vermont birds were among the casualties from this massive mortality event”, said Chris Rimmer, one of the Vermont Loon Recovery Project co-directors for over 20 years. “However, that was pure speculation on our part, as no one knew where Vermont or other New England loons overwintered. That was a real conservation concern for us.”

The recovery of common loon populations in the Northeast is a great conservation success story, but until recently a big piece of the conservation puzzle was missing. No one knew where the loons from these populations spent the winter. What if another catastrophic die-off hit them? Conservationists simply did not know where or what issues to target for management.

A team of scientists comprised of the Upper Midwest Environmental Science Center, the New York State Department of Environmental Conservation, the Wildlife Society, BioDiverisity Research Institute in Gorham, Maine, FLP Energy Maine Hydro and the U.S. Fish and Wildlife Service set out to tackle the problem using new miniaturized satellite telemetry technology.

From 2003 to 2005 the team captured 17 loons in New York, New Hampshire and Maine. The biologists used a boat and a powerful spotlight to slowly approach the loons at night as they floated on the water. When they got close enough, they would quickly dip the net into the water and bring the large bird aboard. A team would be waiting onshore at a portable laboratory where the bird would be anesthetized and the small two inch transmitter and battery pack would be surgically placed under the skin on their back. The thin antenna rose out of their back pointing to the stars ready to signal a passing satellite. The location data was sent to weather satellites on a regular basis for an entire year. The satellites then transmitted the data to processing centers in Maryland and France, where the data was transferred via the internet to the biologists.

They were able to follow ten of the loons from their breeding lakes to the wintering grounds. Most of them traveled non-stop to the Atlantic coast. In-flight location data indicated that they probably fly in a near straight line to their destinations, directly over mountain ranges, rather than along major river valleys. New Hampshire and Maine loons migrated to the nearby coast of Maine, while loons from New York wintered along the coast from Massachusetts to southern New Jersey. What is now clear is that the bulk of the population in the Northeast appears to winter along the Atlantic coast from the Delaware Bay to coastal Maine.

With the latest information in hand, it isn’t Gulf Coast die-offs that now worry biologists in the Northeast. Those loons appear to be from Midwestern and far north populations. It is now oil spills that are of major concern. In January of 1996, the North Cape barge ran aground and spilled its cargo of home heating oil off the coast of Rhode Island. The spill killed more than 400 wintering loons. In April of 2003, a barge struck bottom and spilled its load fuel oil into Buzzards Bay in southeastern Massachusetts, killing more than 200 wintering loons. Most of these loons are now believed to have been northern New England and southern Canada breeders.

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