How birds follow the law of the terraces

It's not just Arsenal and Spurs. Rival groups of birds engage in chanting contests like football fans – and even show fan-like behaviour when the conflict is over, new research has shown.

The losers, especially, appear to commiserate with each other, and senior birds seem to encourage the junior birds in the losing group not to lose heart – or, as one might say, keep their peckers up.

They do it by increased preening of the younger birds, which can be seen as a reward for having performed well in a stressful situation, or an inducement not to leave the group and join another one, according to the study by Dr Andy Radford of Bristol University, reported in Proceedings of the Royal Society B.

The behaviour occurs with a strikingly-coloured southern African species, the green woodhoopoe, which lives in tightly knit groups of up to a dozen individuals with a rigid dominance hierarchy under which only one pair is allowed to breed, and the remaining birds are helpers.

Rival woodhoopoe groups frequently clash and engage in intense calling contests, which can last for anything up to 45 minutes. They do not end in violence, but they do leave one group clearly victorious over the other – as the winning group will invade the territory of the losers and forage for food within it.

"It's a fair comparison with football fans," Dr Radford said yesterday. "The vocal displays are just as raucous, and if the contest really reaches a feverish pitch, it's not unknown for a member of a group to pluck a flower or a piece of lichen, almost as if it were waving a scarf or a flag." Dr Radford is now a rugby fan, but as a boy he supported Scarborough FC, so he knows his football. "I have stood on the terraces and made my voice heard," he said.

His study concerns the aftermath of the contest and invites comparison with post-match commiseration by fans. It focuses on rates of "allopreening" – the preening of one bird by another, a practice thought to reduce stress and strengthen social bonds.

The research shows that allopreening rates are highest in woodhoopoe groups which have the most involvement in chanting conflicts with other groups, and that the birds usually engaged in allopreening after long conflicts, or ones they had lost. In particular, dominant birds increase their preening of subordinates, perhaps encouraging them to stand and fight in future conflicts. Because the biggest groups tend to win, dominants might be providing subordinates with preening in return for the latter's participation.