University of Florida researchers studied the mating behaviors and reproductive success of four captive groups of ibises fed varying levels of mercury during a three-year period, The Miami Herald reported Thursday.
In the first year, the researchers said, 55 percent of the males given the highest doses of mercury in their feed hooked up with other males during breeding season.
"They pretty much did everything except lay eggs," Peter Frederick, a UF wildlife ecologist said. "They built nests, they copulated, they sat in the nests together."
Mercury and other "endocrine disrupters" that affect hormones have shown a range of reproductive impacts on ducks and other birds, Frederick said.
It's not clear exactly what mercury does to the birds, Frederick said.
It may mix up nerve signals or reduce testosterone, giving males what he called a "feminized hormonal profile."
While the study raises concerns about mercury impacts on wildlife, Frederick dismissed the idea of connecting the result to humans, saying that would be a serious misinterpretation.
"Honestly, there is zero relevance for humans," he said.
Copyright 2010 United Press International, Inc. (UPI).