Brood size, sibling competition, and the cost of begging in great tits (Parus major)

Abstract

Evolutionary theory of parent-offspring conflict explains begging displays of nestling birds as selfish attempts to influence parental food allocation. Models predict that this conflict may be resolved by honest signaling of offspring need to parents, or by competition among nestmates, leading to escalated begging scrambles. Although the former type of models has been qualitatively supported by experimental studies, the potential for a begging component driven by scramble competition cannot be excluded by the evidence. In a brood-size manipulation experiment with great tits, Parus major, we explored the scramble component in the begging activity of great tit nestlings by investigating the mechanisms of sibling competition in relation to brood size. While under full parental compensation, the feeding rate per nestling will remain constant over all brood sizes for both types of models; the scramble begging models alone predict an increase in begging intensity with brood size, if begging costs do not arise exclusively through predation. Great tit parents adjusted feeding rates to brood size and fed nestlings at similar rates and with similar prey sizes in all three brood-size categories. Despite full parental compensation, the begging and food solicitation activities increased with experimental brood size, whereas nestling body condition deteriorated. These findings support a scramble component in begging and suggest that the competition-induced costs of food solicitation behavior play an important role in the evolution of parent-offspring communication.

An Experimental Test of a Causal Link between Problem-Solving Performance and Reproductive Success in Wild Great Tits

“…When we could not match three broods, we used duos by skipping the control treatment (nest B), and when more broods could be matched, we used quadruplets of nests by repeating the control treatment (nest B). In great tits, the number of native vs. foreign nestlings in a nest does not affect provisioning rate (Neuenschwander et al, 2003).…”

Benefits associated with escalated begging behaviour of black-billed magpie nestlings overcompensate the associated energetic costs

“…For example, the effect of sibling competition (e.g. Johnstone, 1999;Rodríguez-Gironés, 1999;Royle et al, 2002;Neuenschwander et al, 2003), the possible costs related to the nestling vigilance for parent arrival (Roulin, 2001) or those costs suggested for behaviours related to sibling negotiation during the absence of parents (Johnstone and Roulin, 2003). Moreover, because cyproheptadine would exclusively affect hunger level, this experimental approach allow us to disentangle the effects of body condition and nestling hunger level on begging behaviors (e.g.…”

Acoustic parameters of begging calls indicate chick body condition in Wilson’s storm-petrels Oceanites oceanicus

“…Most studies on begging behaviour have taken place in passeriform birds, and based on the results it may well be that chicks convey information on their nutritional needs (Iacovides and Evans 1998;Kilner and Johnstone 1997;Price and Ydenberg 1995;Redondo and Castro 1992). However, these results were partly clouded by the fact that begging behaviour is also influenced by nestling competition (Neuenschwander et al 2003;Price 1996), previous feeding experiences (Kedar et al 2000;Rodriguez-Girones et al 2002) and predation pressure (Briskie et al 1999). …”