For whom does the hen cackle? The function of postoviposition cackling

In birds, the time immediately after oviposition has been assumed to be par ticularly favourable for an insemination to fertilize eggs. Based on this a ssumption, Thornhill (1988, Verhandlungen der Deutschen Zoologischten Gesel lschaft, 81, 145-154) suggested that a particular vocalization, the postovi position cackle, of female fowl, Gallus gallus, signalled a peak in fertili ty, which incited male sexual behaviour and resulted in females copulating with the most dominant males. It may therefore benefit females by indirectl y selecting for competitive copulation partners. We tested this hypothesis in a free-ranging population of feral fowl. Contrary to the hypothesis, we found that: (1) postoviposition cackling was associated with a significantl y lower probability of a female obtaining a copulation; and (2) males did n ot respond any differently to the experimental playback of the postoviposit ion cackling and a control call. These results are consistent with the peri od immediately after oviposition being an unfavourable time for an insemina tion to fertilize eggs. One function of postoviposition cackling may thus b e to avoid the costs of sexual harassment by signalling to males a particul arly unsuitable time for fertilization. (C) 2001 The Association for the St udy of Animal Behaviour.