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Not in the mood, egrets skipping sex after eating bad fish

Methylmercury accumulating in aquatic creatures

An egret is seen flying on the 16th hole at Sea Island's Seaside Course.
An egret is seen flying on the 16th hole at Sea Island's Seaside Course. (Photo by Sam Greenwood/Getty Images)

MIAMI – Florida’s great egrets just aren’t in the mood. Blame it on a headache or stomachache caused by eating some bad fish. A University of Florida study found increased mercury exposure is turning egrets off from sex.

Mercury contamination led to a 50% reduction in the birds' attempts to breed, meaning the heavy metal is affecting their reproduction process much earlier than previously thought. The study also noted the full effects of mercury exposure among wading birds may be “systematically underestimated."

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The Miami Herald reported that heavy metals and other contaminants can disrupt hormones, which can then impact a desire to breed. Certain microorganisms can change mercury into methylmercury, a highly toxic form that builds up in fish, shellfish and animals that eat fish, in a process known as bioaccumulation. Most human exposure to mercury is from eating fish and shellfish contaminated with methylmercury.

“This study suggests that there are a lot of birds that are just sitting out the breeding season. It’s not that they are starting and not successfully finishing; they aren’t even attempting to breed,” said Peter Frederick, one of the study’s co-authors.

The study, which relied on more than 20 years of data, was published in the peer-reviewed scientific journal Environmental Science & Technology. Researchers counted nesting pairs in about 130 colonies of great egrets using aerial and land surveys.