Birds in Africa post their fellow warblers on sentry duty where they sing a song of reassurance to their foraging friends, researchers report.

One pied babbler gives a distinctive watchman’s song, which makes other birds more comfortable in their feeding, the researchers from the UK’s University of Bristol discovered.

“These exciting results point to a great example of true cooperation,” says Andy Radford (press release). “The unselfish behaviour of the sentry is probably rewarded down the line by the improved survival of group mates, which leads to a larger group size. This increases the sentinel’s chances of survival when the group is under attack from predators or having to repel rivals from their territory.”

Radford’s team found that birds who heard recordings of the watchman’s song spent less time looking for predators and spread out more widely. This meant that they caught more food, the team showed.

The pied babblers used in the study are accustomed to researchers so they could be closely observed when foraging. They are, in fact, so well trained that they fly to researchers in response to a whistle and weigh themselves on a set of scales. If only they could write research papers too….

The research has been published in Current Biology.

Press coverage

Birds smart enough to stand guard, say scientists at University of Bristol – The Times

Birds post a sentry when foraging for food – The Daily Telegraph

Image: pied babbler / Andy Radford