Researchers believe poisonous metal compounds entering the food chain can affect bird sexuality, causing a reduction in offspring. This is the first scientific study to show how pollutants alter sexual preferences.
Scientists found that even relatively low levels of methylmercury in the diet of male white ibises caused the birds to pair up with each other, snubbing females, reports the Daily Mail.
Methylmercury is a form of mercury. It has been seeping into groundwater from industry for years.
Peter Frederick from Florida University in the US captured 160 young white ibises, a coastal wading bird, and gave them food laced with methylmercury.
The birds were split into four groups. One group ate food with 0.3 parts per million (ppm) methylmercury, which most American states would regard as too high for human consumption.
A second group was fed 0.1 ppm, and the third 0.05 ppm. The fourth group was not given the substance.
All three groups which were given methylmercury had significantly more homosexual males than the control group. Male-male pairs courted, built nests together and paired off for several weeks.