Male cuckoos appear to have a unique call that makes them distinguishable to and from other males. A new study appearing in Animal Behaviour shows that an individual cuckoo call may determine how a male responds to an interloper in his territory—behaving more tolerantly towards neighbours and more aggressively towards strangers.
Common Cuckoos, Cuculus canorus, are brood parasites: they lay their eggs in the nests of other bird species, and let these hosts incubate their eggs and feed and rear the nestlings. Although cuckoos do not show parental care, they demonstrate complex social behaviour, including territoriality and male-male aggression. Cuckoos have a well-known and simple two-phrase call ("cu" and "coo"), uttered by males during the breeding season. Previous studies have suggested that the "cu-coo" call of males is individually unique, allowing discrimination between different classes of males.