Quality vs. quantity: energetic and nutritional trade-offs in parental provisioning strategies

摘要: 1.  When faced with increased brood demand, parent birds provisioning young in the nest can make a variety of adjustments to their foraging and food allocation strategies. Logical extensions classic optimal theory predict effort larger broods be accompanied by changes load size, distance from nest, as well possible type size prey delivered. 2.  We assessed such behavioural consequences pairs European starlings (Sturnus vulgaris) responding range experimental sizes. Parents feeding visit rates spending less time nestbox around colony. High were also associated loads per delivered nest. As consequence, chicks large small received similar intake, but experienced differences nutritional quality food. sizes able increase despite same sites, travelling at comparable flight speeds maintaining body masses parents smaller broods. 3.  Parental energetic expenditure, measured through doubly labelled water analyses, showed no effect treatment. The greater proportion indigestible material gram (i.e. soil guts earthworms) was probably responsible for fact that these grew slower fledged lower masses, although we cannot rule out possibility growth due higher costs sibling competition within Lighter fledglings disappeared local area earlier summer, result differential mortality rather than premature natal dispersal. 4.  We discuss adaptive significance trade-off between quantity items reference natural variation conditions demand.