Loon and Her Chick

New York's Adirondack Mountains.

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Photo By: Wildlife Conservation Society

An extensive study of New York’s Adirondack loon population has revealed that mercury contamination can lead to population declines of the iconic bird. The research effort was a joint project between the New York State Energy Research and Development Authority (NYSERDA), Biodiversity Research Institute (BRI) and the Wildlife Conservation Society (WCS).

For nearly 10 years, researchers from these organizations followed mercury contamination throughout the aquatic food chain, from zooplankton to the Common Loon, in Cranberry and Lows lakes as well as in other bodies of water. They found that loons with elevated mercury levels produced significantly fewer chicks than those with low mercury levels, particularly those breeding on the more acidic lakes that are common in the Adirondack Park.

The most common way mercury contaminates the environment is from burning coal for power or industry, like cement. Because the Adirondacks are set downwind of major industries and power plants throughout the midwest, contamination fallout is high. Mercury is a neurotoxin that can cause brain damage in children who are exposed, most often in utero, through mother's milk, or through eating contaminated fish.

Winds carry the pollutant from distant point sources. Adirondack lakes—where aquatic loons live and raise young—are exposed to mercury contamination deposited in the environment. Mercury is toxic at even small levels, and accumulates in animals as it progresses up the food chain. Loons feed at the highest level in the food web, which increases their risk of the toxic effects of mercury exposure.

Scientists found that mercury was present in loons at a level that put the birds at risk of reproductive harm—21 percent of male loons studied and 8 percent of females were at a high risk of behavioral and reproductive impacts based on the levels of mercury in their bodies.

Adult loons with high mercury levels also lack good parenting skills, for example, these birds do not incubate eggs consistently enough for chicks to hatch. Thus, the high mercury birds experienced lower reproductive success than the low mercury birds because of the reduced hatching rate of the eggs.

In December of 2011, the U.S. Environmental Protection Agency (EPA) finalized the Mercury and Air Toxics Standards Rule that requires coal-fired power plants to update their mercury pollution control technologies. However, overseas emissions are also a problem. BRI scientists have been involved in helping to inform mercury emissions policy on both domestic and international levels.

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