 The pollutant methylmercury is a globally distributed neurotoxin and an endocrine system disruptor . In the Everglades ecosystem , human pollution has led to increased concentrations of methylmercury , which have impacted the behaviors of the American white ibis . Hormone levels in males are affected , leading to a decrease in the rates of key courtship behavior , and fewer approaches by females during the mating season . In addition , methylmercury also increased male @-@ male pairing behaviors by 55 % . Both the chemically induced " homosexual " behavior and the diminished ability to attract females by males have reduced reproduction rates in affected populations . Exposure of American white ibises to methylmercury causes reduced foraging efficiency and it also makes them more likely to abandon nests owing to the disruptive effect of the pollutant on the bird 's hormone systems , which in turn affects parental care behavior . Tests on captive birds have not shown a decreased survival of American white ibis exposed to methylmercury . 
