Birds show greater "solidarity" when preparing for conflict with rival groups, research by a university in Bristol has revealed.
A study of birds behaviour surrounding conflict conducted by the University of Bristol found birds may be capable of anticipation and future planning - a trait that was until recently considered the preserve of humans and other primates.
Dr Andy Radford, from the University's School of Biological Sciences, studied a population of green woodhoopoes, common forest-dwelling birds in southern Africa, for the research.
Green woodhoopoes, which live in groups of up to 12 individuals, frequently preen each other to promote social cohesion within the group.
The new research, published on Wednesday in Biology Letters, found dominant group members increase their preening of subordinate members when moving into areas where clashes with other groups are likely.
"It's a case of scratching your back if you cover mine", Dr Radford said.
"Self-directed behaviour would indicate stress, whereas the increased preening of subordinates by their superiors is likely to be a deliberate social behaviour when the threat of conflict is higher."