The findings, published in the journal Current Biology, suggest that the distinctive watchman's song of the pied babblers is a rare example of cooperative behavior in the animal world, the University of Bristol said in a release.

"The unselfish behavior of the sentry was rewarded further down the line by the improved survival of individuals, which in turn leads to a larger group size," researcher Andy Radford said in a statement. "This increases the sentinel's chances of survival when the group is under attack or having to repel rivals from the territory."

Radford said when a sentry bird was present the group was able to spread out more and spend more time in the open, allowing the group to catch bigger and better prey.