Alloparental behaviour in Mute Swans Cygnus olor detected by DNA fingerprinting

Abstract

A pair of Mute Swans was located on the River Ivel in England that were accompanied by an unusually large number of cygnets. The application of DNA fingerprinting to blood samples taken from the birds revealed that the cygnets comprised two sets of cygnets. Nine cygnets were the genuine progeny of the attendant adults. The other six were full siblings among themselves, and were related less closely to the remainder. It is suggested that six cygnets were adopted from an adjacent family, one of whose parents was probably related to the adopting male.