Mollymawk

Abstract: The vocal repertoire of Diomedea bulled is described. A low croaking note given by both sexes was the commonest vocalisation and a loud wail uttered with wide open bill was used by male and female during conflicts and by the male in courtship. Four kinds of low frequency groaning noises and five sharp percussion sounds produced by contacts between bill or mandibles were also used. In preliminary experiments with models and sound playbacks, visual or vocal stimulation alone evoked very few responses from lone birds on nests but all tests made with an advanced model combined with playbacks induced a croaking response. It was concluded that the contagious nature of the croaking display resulted from both visual and vocal stimuli. Some comparisons showed that the repertoire of this albatross is similar to those of other medium-sized albatrosses and some apparently homologous vocalisations are also heard from the large D. exulans and D. epomophora. The calls of the north Pacific species D. albatrus, D...