To figure out the effect that these pharmaceuticals have on birds, the researchers first had to figure out how much fluoxetine is typically found in worms and bugs at sewage treatment plants. When paired with female starlings that had been eating the Prozac-laced worms, males only sang half as often and for half as long as they did when they were paired with a female that hadn’t been exposed to the drug. Male starlings were also much more aggressive toward female starlings that had been exposed to low doses of Prozac, the researchers found.
– We humans consume a lot of antidepressants, and that means birds inadvertently do the same while feeding at sewage plants. Now researchers in the UK suggest that it's taking a toll on the birds' libidos, making them—or at least the females—less attractive to prospective mates. In their study, researchers at the University of York focused on starlings in captivity. They fed the birds worms laced with Prozac, on par with what their counterparts in the wild might pick up while eating worms and insects at sewage plants, and then watched what happened. Dosed males didn't change much, but dosed females suddenly seemed less attractive to the boys. Male starlings sang less frequently to them and treated them more aggressively—pecking, tugging at feathers—than is typical in the wooing phase. It's "the first evidence that low concentrations of an antidepressant can disrupt the courtship of songbirds," says study co-author Kathryn Arnold in a release. "We're definitely not saying that it's bad to take antidepressants, but certainly there is a greater need for new technologies to clean out sewage," she elaborates to the Washington Post. Presumably, the same type of behavior occurs in the wild, but researchers note that it's hard to replicate for a not-so-great reason: Wild birds are dining not just on Prozac but on a whole cocktail of pharmaceuticals, and the study adds to evidence that growing concentrations of them "can alter important traits related to individual fitness and population dynamics," per the study. (Drawings of a cockatoo revealed a medieval surprise.)