Bird populations are being threatened by water pollution, which is leading to male-male mating behaviors.
Researchers suggest that the presence of toxic metal compounds in the food chain may interfere with sexual behaviors, ultimately reducing reproductive success.
Their studies revealed that even minimal exposure to methylmercury in the diet of male white ibises resulted in these birds choosing partners of the same sex over females.
Methylmercury, a liquid metal at room temperature better known as quicksilver, has been contaminating groundwater due to industrial activities for many years.
This research marks the first scientific evidence indicating that this pollutant may influence sexual orientation.
Peter Frederick, a researcher from the U.S., captured 160 young white ibises—a type of coastal wading bird—and fed them food contaminated with methylmercury.
The subjects were divided into four categories. One group consumed food containing 0.3 parts per million (ppm) of methylmercury, a level deemed excessive for human safety in most U.S. states.
The second group was administered 0.1 ppm, while the third group received a low dose of 0.05 ppm, which is commonly encountered by wild birds. The control group was provided food free from the toxin.
Significantly higher occurrences of homosexual pairings were observed in the three dosed groups compared to the control group. Male-male pairs engaged in courting behaviors, constructed nests together, and remained partnered for several weeks.
The impact was more pronounced with higher doses, affecting 55 percent of males in the 0.3 ppm group.
In total, male-male mating accounted for 81 percent of nonproductive nests within the groups exposed to the doses.
‘While we were aware that mercury could lower testosterone levels,’ Dr. Frederick stated, ‘this outcome was unexpected. In the most extreme case, there could be a 50 percent decline in offspring production.’ He indicated that similar effects could potentially affect other bird species as well.
Nonetheless, Dr. Frederick from Florida University and his colleague Nilmini Jayasena from Peradeniya University in Sri Lanka acknowledged that the association between methylmercury and analogous effects in mammals remains largely uncertain.
by David Livingstone
