Pharmaceuticals in the environment are a recently identified global threat to wildlife, including birds. Like other human pharmaceuticals, the antidepressant fluoxetine (Prozac) enters the environment via sewage and has been detected at wastewater treatment plants. Birds foraging on invertebrates at these sites can be exposed to pharmaceuticals, although the implications of exposure are poorly understood. We conducted experiments to test whether chronic exposure to a maximally environmentally relevant concentration of fluoxetine (2.7 μg day−1) altered courtship behaviour and female reproductive physiology in wild-caught starlings (Sturnus vulgaris), a species commonly found foraging on invertebrates at wastewater treatment plants. When paired with a female over two days, males sang less and were more aggressive towards fluoxetine-treated females than controls. Fluoxetine-treated females were initially aggressive towards males, becoming significantly less aggressive by the second day. In contrast, control females expressed intermediate levels of aggression throughout. We found no effect of female treatment on female courtship behaviour. Female body condition, circulating testosterone and circulating oestradiol were unaffected by treatment and did not account for male preference. Our findings suggest that exposure to an antidepressant reduced female attractiveness, adding to growing evidence that environmental concentrations of pharmaceuticals can alter important traits related to individual fitness and population dynamics. ||||| 
 
 A starling. (Daniel Baleckaitis/University of California at San Diego/AP) 
 
 It’s been well-documented that a decreased sex drive can be one of the side effects of antidepressants like Prozac. But the amount of these drugs that end up in sewage plants may also have an impact on the mating habits of wild birds, a new study from the University of York shows. 
 
 Researchers found that female starlings that had been exposed to small doses of fluoxetine, the generic name for Prozac, became less attractive to male starlings, which sung to them less often and treated them more aggressively. Kathryn Arnold, one of the study’s authors and a senior lecturer in ecology at the University of York, described it as “the first evidence that low concentrations of an antidepressant can disrupt the courtship of songbirds.” 
 
 That’s problematic because birds that are slow to find a mate may not get the chance to breed, she wrote. 
 
 “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,” Arnold told The Washington Post. 
 
 Birds like to graze at sewage treatment plants, which are teeming with worms, flies and maggots, she explained. But because antidepressants often make their way through the human body and into sewage plants without fully breaking down, those insects are frequently laced with prescription drugs. 
 
 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. They then replicated that, dosing worms with a low concentration of Prozac — less than 10 percent of what a human would be given for therapeutic purposes, Arnold said. 
 
 The Prozac-treated worms were fed to starlings living in outdoor aviaries that mimicked the natural environment as much as possible while keeping the birds in captivity. The following spring, during breeding season, male starlings were “set up on essentially blind dates,” Arnold said. 
 
 The results were striking. 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. 
 
 That’s significant, Arnold said, because singing is an important part of birds’ courtship rituals, and is used to judge potential mates. “The equivalent of reduced libido, in a wild animal, is how they behave during courtship,” she said. 
 
 Male starlings were also much more aggressive toward female starlings that had been exposed to low doses of Prozac, the researchers found. 
 
 “They chased them, they pecked them, they tugged on their feathers,” Arnold said. 
 
 Interestingly, female starlings didn’t seem to be turned off by male starlings that had consumed small amounts of Prozac. Arnold credits that to the fact that the male starlings’ behavior didn’t change drastically, while female starlings seemed less interested in the opposite sex and were often inconsistent in their behavior. 
 
 “They were blowing hot and cold,” she said. “They could be aggressive, and they could be passive.” 
 
 Could this result in fewer baby birds being born and, ultimately, a decline in the number of starlings? Arnold said it’s possible, but further research is needed to determine if the same behavior that her team witnessed is also happening in the wild. Complicating the question is the fact that birds aren’t just being exposed to Prozac — they’re also potentially ingesting a whole slew of other drugs that have ended up in the sewage system. 
 
 “There is growing evidence around the world that shows that we need to be taking a look at what it is we’re pumping out,” she said. “These cocktails of pharmaceuticals are drugs that your medical provider would never prescribe in combination with one another.”
– 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.)