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"Peter Frederick, an ecologist at the University of Florida, Gainesville, and his colleagues collected 160 white ibis nestlings from breeding colonies in south Florida in 2005, and split them into four groups, each composed of 20 males and 20 females. Once the birds were 90 days old, the researchers began adding methylmercury to their feed. Three of the groups were given low, medium or high doses of mercury based on levels ranging from 0.05–0.3 parts per million recorded in the wild, while the fourth group were given no mercury.
Over the next three years, the researchers measured mercury levels in the feathers and blood of the ibises, and observed their mating behaviour.
The team found that the levels of mercury built up in the birds over time, and that exposure resulted in roughly 13–15% more nests failing to produce any offspring. A high proportion of these failed nests were found to be male-male pairings. "
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