Female Birds Given Antidepressants See Males Sing Less And Peck More at Them

Researchers found that male starlings courted females on Prozac less and exhibited more aggression toward them.
Loukia Papadopoulos

The singing habits of birds have long fascinated scientists. Many studies have been conducted on the subject revealing unique insights into the species' behaviors.

Urban birds have been found to sing less during noisy periods and to even switch to night-time singing in order to be heard. When it comes to singing for mating purposes, birds have even observed orchestrating duets to deter cheating and engaging in secretive nightly liaisons.

Now, a new study by the University of York has revealed perhaps the oddest of all birds' behaviors. The males of these flying feathered creatures, it turns out, are less attracted to females who are on antidepressants, singing less at them and pecking more. 

Birds on Prozac

The study tested birds on dilute concentrations of Prozac similar to those measured at sewage works. Birds are often exposed to pharmaceuticals because their diets consist of insects contaminated by these substances due to their release in sewage treatment plants.  

Antidepressants compounds break down slowly when eliminated through the body and can, therefore, stay active for a while in sewage systems. And there is no shortage of these compounds!

In 2010, 23.3 million people in the US alone were prescribed antidepressants and that number only continues to riseThis could prove a concern for birds said the study's researcher Sophia Whitlock, from the Environment Department at the University of York. 

“Singing is a key part of courtship for birds, used by males to court favored females and used by females to choose the highest quality male to father their chicks. Males sang more than twice as often and as long to untreated females compared to females that had been receiving low doses of Prozac," explained the scientists.

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Whitlock and her partner Dr Kathryn Arnold, also from the Environment Department at York, have been studying the effects of Prozac on starlings for several years. In addition to less courting, their work revealed even more troublesome changes in behavior.

The researchers also reported increased male aggression towards the females exposed to antidepressants. The males were likely to exhibit violent behavior towards the female test subjects including chasing, pecking and even clawing at them.


All in all the effects are harmful to the species' mating patterns. “Here is the first evidence that low concentrations of an antidepressant can disrupt the courtship of songbirds," said Arnold.

"This is important because animals that are slow to find a mate often won’t get to breed. With many wildlife populations in decline, we have to ask whether more could be done to remove chemical contaminants like pharmaceuticals from our sewage," she warned.

The study was funded by the Natural Environment Research Council (NERC) and published in the journal Chemosphere.