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Pattern of avian growth are highly variable within species and populations, depending on a variety of environmental factors. Although growth rate has important consequences on offspring fitness, relatively little is known about behavioural and physiological mechanisms underlying the growth processes. In this project, we use a novel approach by examining the impact of environmental stress on nestling growth patterns through changes in parent-offspring communication. The objectives of this study are to examine (1) the impact of environmental stress (via food shortage and increased predation risk) on parental behavioural strategies that increase sibling competition (maternal effects, hatching asynchrony, selective feeding of chicks), (2) the interactions between offspring begging display and variability of growth patterns, (3) the impact of environmental stress on selectivity of resource allocation to specific body structures and physiological costs of selective allocation (reduced immunity, delayed ossification of bones) in chicks, (4) parent-offspring behavioural interactions and physiological stress in chicks in response to different types of predators (nest predators and predation risk outside the nest). As a model species, we use two passerines, the great tit and the pied flycatcher, that have different life-histories. Both experimental and comparative methods will be used to address the above questions. The outcome of this project is to provide new ideas and explanations for several essential questions in evolutionary ecology. For instance, selective allocation of resources to different body structures can be a mechanism aimed to maintain normal (targeted) growth of vital body structures even in stressful conditions. The results will be published in international peer-reviewed journals. |