Begging as graded signals of need for food in young ring-billed gulls.
Recent models suggest that begging vocalizations are honest signals communicating a chick's nutritional needs to its parents. We investigated the effects on begging of short-term food deprivation ('hunger') and long-term reduction in body condition under controlled laboratory conditions in ring-billed gulls, Larus delawarensis. We tested two condition groups (high: fed to satiation; low: fed 75% wet mass of high-condition diet) at three levels of short-term food deprivation (1, 4 and 12 h). Begging call rate, intensity and peck rate were significantly greater in the low-condition chicks. Begging in both high- and low-condition groups increased with short-term deprivation, tending to asymptotic levels by 12 h of deprivation. Overall level of begging was graded according to both short- and long-term need for food, with steep slopes at the beginning of the begging curves providing a strong basis for parental discrimination of signalling level. The system appears to agree with the design requirements of a homeostatic control system, and with predictions of current game-theoretic models of honest signalling. Possible effects of sibling competition and parent-offspring conflict are discussed. These issues require further study under natural conditions in this species. Copyright 1998 The Association for the Study of Animal Behaviour.
Department of Zoology, University of Manitoba
S
Iacovides
RM
Evans