Loons of the Adirondacks

Loon Banding Photo
After quickly banding and examining a common loon, a WCS scientist places the bird back into the lake.
©WCS Adirondack Program

In upstate New York’s Adirondack Mountains, common loons spend their long lives eating fish, swimming and breeding in freshwater lakes, and flying hundreds of miles to the East Coast for the winter. The loons’ behavior brings them into contact with water and air contaminants, so the health of these birds can often reflect the health of the overall environment. WCS-Global Health, WCS-Adirondacks, and BioDiversity Research Institute (BRI) track, band, monitor, and take blood samples from these large birds to check their exposure to disease and pollution.


Coal-burning power plants emit mercury particles, which can fall into bodies of water and become methylmercury, a harmful neurotoxin, particularly in many acidic lakes found in the Adirondacks. Microorganisms consume the toxic particles, which then travel up the food chain and accumulate in the bodies of fish in larger and larger concentrations at each step. Loons eat fish. Recently, WCS researchers found that Adirondack loons with high levels of mercury fledge about 40 percent fewer chicks compared to loons with lower levels of the neurotoxin. Contributing to these birds’ plight, the toxin can make the birds sluggish, causing them to catch fewer fish. Pesticides and infectious diseases also threaten Adirondack loons.


  • Assess the health of loons in the Adirondacks
  • Investigate loon immunology, in collaboration with Michigan’s Calvin College, to determine the birds’ immune responses to various infectious diseases
  • Test loons for avian viruses, including avian influenza
  • Evaluate contaminants in eggs, such as flame retardants and other persistent organic pollutants (POPs)
  • Monitor the toxin mercury effects on loon reproductive success

What WCS is Doing

Every summer since 2003, WCS and BRI researchers have been catching, color-banding, weighing, measuring, taking samples from, and then releasing loons in the lakes of New York’s Adirondack Park. The blood sample analyses show whether the birds have been exposed to pollutants, pesticides, and disease, and how their organs are functioning. Over the course of each summer, field staff monitor the birds’ reproductive success. WCS experts and volunteers throughout New York participate in an annual loon census in late July to record the status of and track trends in the state’s loon population.

From the Newsroom

Mercury Sickens Adirondack LoonsJune 28, 2012

Loons nesting and raising their young in the New York Adirondacks are increasingly threatened by mercury contamination, which impacts reproduction and behavior. A new scientific report on Adirondack loons emphasizes the importance of reducing mercury in the atmosphere.

Adirondack Alarm CallMarch 7, 2008

A long-term study by the Wildlife Conservation Society, the BioDiversity Research Institute, and other organizations has found and confirmed that environmental mercury—much of which comes from human-generated emissions—is impacting the health and reproductive success of common loons in the northeastern U.S.

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