A ten-year study of the Bustard, a bird known for its complex and energetic courtship displays, showed a massive decline in sperm quality in the most 'showy' birds. Scientists, writing in the journal, Ecology Letters, believe that this decline in fertility is a direct result of early aging.

During the study, the scientists looked at 1,700 North African Houbara Bustards and found that every time a male Bustard performed the mating ritual, known as 'booming', the quality of their sperm declined. The researchers hypothesised that the male bird put so much energy into the mating ritual that it aged much faster.

The Bustard energetic mating ritual consists of preliminary strutting followed by the erection of an ornamental shield of plumage while running at high speed. Some birds were seen to 'boom' for up to 16 hours per day in an activity that clearly used up a lot of energy.

"Over the age of six years they began to produce much smaller ejaculates with immobile and frequently abnormal sperm," said lead researcher at the University of Burgundy in France, Dr Brian Preston. "But the key finding was that males that had invested most effort displaying to females in their earlier years experienced the onset of this age-related decline in fertility at a younger age. They effectively seemed to burn themselves out sooner."

Houbara Bustards were selected for the project, as it was known to be a species with a long lifespan. As a result, it was possible to study birds aged from one up to 24. At the conclusion of the study, the scientists put forward the theory that because the birds lived in a habitat with many predators, they evolved a mechanism by which they put more energy into mating in early life - a form of biological trade-off that resulted in premature aging.

Clearly, it's possible that the same evolutionary mechanism exists for other species. Whether or not the phenomenon extends to human males who flirt excessively is a question that will probably require more study.

Top Image: Bustard - Credit: © Steffen Foerster | Dreamstime.com