Study finds cheating boosts male sparrow fitness

Cheating pays. Or at least it does for male sparrows, according to new research.

A team, led by Dr. Julia Schroeder and Dr. Jamie Dunning from the Department of Life Sciences, found that male sparrows that cheat on their social partner have a higher life-time fitness—the ability to survive and reproduce.

The study is published in Animal Behaviour.

This has been traditionally difficult to study, because in wild populations, offspring fathered outside a bonded pair can be hard to track, and some birds will simply leave the area, making it unclear what age they die.

The team studied the sparrows of Lundy Island, which hosts a ‘closed’ population, meaning that no individuals leave or arrive. This allows the team to collect lots of accurate data on the inhabitants, including their ages and breeding success, which have been recorded for 25 years.

They found that males that had offspring both with their bonded female and outside that relationship had the highest fitness, while “floating males,” which only had non-bonded offspring, had the lowest lifetime fitness.