ProjectsLakes and PondsCommon Loon ConservationCommon Loon ResearchResults

Common Loon Research Results

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Mortality Studies

VCE’s Vermont Loon Conservation Project sends all recovered deceased loons to Tufts University Wildlife Veterinary Program to determine the likely cause of mortality. Since the 1980s, researchers at Tufts have necropsied more than 1,500 loons. Their work has revealed that lead fishing gear was the highest single source of mortality of adult loons in New England. This directly led to legislation to reduce the exposure of wildlife to lead. The studies have also helped us track rates of naturally occurring diseases, motorboat hits, fights with intruder loons, and other causes of mortality.

Population Modeling

Vermont and New Hampshire now boast the most complete and longest-running loon population data sets anywhere in the world. We’re using these to determine what factors cause loon populations to rise or fall.  Our modeling, for example, has demonstrated that nest rafts, warning signs, and rescues of loons in distress have a significant role in loon recovery, conservation, and population growth.  We’re also using the data to evaluate how recreational boating and fishing might affect loon populations.

Mercury Toxicity

VCE and our colleages have determined that mercury presents a genuine but low-level risk to Vermont loons. Troubling hotspots appear to be reservoirs, where sediments can breed bacteria that help convert elemental mercury to its toxic form (called methymercury). By sampling blood and feathers over the course of our conservation work with loons, VCE has contribted to a huge body of research on mercury and Common Loons. We’ve also collected eggs that fail to hatch for use in loon research.

Climate Change

The longer we study loons, the more we can understand what a warming planet means for these birds. We can determine whether loon populations are shifting distribution or suffering from climate change’s impacts on lake ecology, fish populations, and water level changes during big storms. All these can affect Common Loons. We can even gather data on whether warmer springs – even spring heat waves – can cause loon nests to fail during egg incubation.

Other Threats

VCE’s attention to nesting loons across the state can help us understand other threats, including what seems to be the disappearance of territorial pairs from some lakes in northern New England. Elsewhere, we’re watching for botulism outbreaks, which have threatened loons on the Great Lakes. These outbreaks seem to be associated with non-native Zebra Mussels, Quagga Mussels, and a fish called the Round Gobi. Even two oil spills off the New England coast in the past two decades were a cause for concern because Vermont’s loons winter off the New England coast.