The close quarters of a rookery can be a lot like a crowded row-house neighborhood: Every now and then, there's bound to be a fight. And after a nasty squabble with a neighbor, what better way to smooth those ruffled feathers than with a kiss at home? Bill-twining, which looks remarkably like kissing, is rooks' chosen way to ease their tempers, reports experimental psychologist Amanda Seed from the University of Cambridge, United Kingdom. Such behavior has long been known among primate species, such as chimpanzees, but this is the first time it's been documented in birds.
Animal behaviorists have studied squabbling among numerous mammalian species, particularly primates, which after a fight often seek comfort through mutual grooming with an animal not involved in the row. This tactic is believed to reduce stress. Chimps, bonobos, and a few other mammals go a step further: They even engage in grooming or other forms of affiliative behavior with their opponent, which is seen as a form of reconciliation.
In the wild, rooks nest in treetops with thousands of rook neighbors. Pairs typically mate for life and return to the same nesting site each year, giving the group a degree of social permanence. A big social group has its advantages--more eyes to watch for predators and to find food--but there are also drawbacks: Every rook wants the best sticks to build their nests, and the best morsels of food. "It's like walking a tightrope, trying to find a balance between those group benefits and your own," says Seed, "and of course that leads to arguments."
Seed videotaped and studied post-conflict behavior in a captive group of 10 rooks, which includes four monogamous pairs, watching to see if the birds sought solace from other birds after a fight. Although paired rooks did not fight with each other, individuals often quarreled with neighbors, squawking and flapping over a contested stick or bit of food. After such fights, the antagonists flew to their mates. The pairs preened, shared bits of food, and twined their bills, Seed reports in the January 23 issue of Current Biology. They did not make up with their opponents, however.
The rooks' kiss-and-calm-down behavior with their socially valuable mates has "remarkable similarities to behaviors among the great apes," says animal behaviorist Filippo Aureli at Liverpool John Moores University, U.K. But Emory University's Frans de Waal (who discovered reconciliation and consolation in chimpanzees) notes that the birds may not actually be consoling their mates, an act requiring that they initiate the calming kisses. Nevertheless, he's pleased to see birds added to "the long list of animals that try to manage stress caused by conflicts in their societies."