The function of triumph ceremonies in the black swan

The function of triumph ceremonies was investigated in the socially monogamous black swan, Cygnus atratus. Paired black swans regularly performed triumph ceremonies, most of which were initiated by the male. We found no difference in the frequency with which ceremonies were performed by pairs prior to the breeding season compared to pairs with dependent cygnets. Pairs with more cygnets tended to perform fewer triumph ceremonies and the number of triumphs performed by a pair did not correlate with the survival of their cygnets. Feeding experiments showed that the frequency of triumph ceremonies performed by pairs increased when many swans were in close proximity. Pairs also performed triumph ceremonies in response to the playback of a triumph ceremony by another pair, but not in response to playback of an advertisement call by an unpaired black swan. We suggest that our results are compatible with the pair formation and collaborative threat hypotheses, but not with the bond-maintenance hypothesis.