BEGGING SIGNALS AND BIPARENTAL CARE - NESTLING CHOICE BETWEEN PARENTAL FEEDING LOCATIONS

The evolutionary conflict over the amount of resources transferred bet ween a parent and its offspring may be resolved by honest signalling o f 'need' by offspring and parental investment in relation to signallin g level. In birds, biparental care is the norm and evidence that male and female parents differ in their investment pattern in individual of fspring is growing. In an experiment on great tits, Parus major, we in vestigated how and why parents differ in food allocation when respondi ng to similar chick signals, which supposedly uniquely reflect the chi ck's nutritional condition. Nestling hunger level was manipulated by f ood deprivation and hand-feeding. Subsequent filming revealed that par ents fed from significantly different locations on the nest and thereb y forced chicks to choose between them when competing for favourable p ositions. Deprived nestlings approached, and fed ones retreated (or we re displaced by siblings) from, positions near the female. No such beh aviour was observed towards the male. Females allocated more feeds tha n males to the food-deprived nestlings. The results are discussed in t erms of nestling competition for access to 'begging patches'. By varyi ng their 'begging patch' value, parents may exploit competitive inter- sibling dynamics to influence the outcome of competition among chick p henotypes (e.g. 'need', size, sex). Parent birds may thereby exert con siderable control over the information content of chick begging behavi our. (C) 1998 The Association for the Study of Animal Behaviour.