The role of food availability in determining the energetic and life history costs of reproduction in short-lived birds

Abstract

Food availability strongly affects avian breeding success. Conflicting results from food supplementation studies have obscured the role of food availability in shaping the life
history trajectories of birds. With the popularity of providing food for wild birds increasing, the effects of this resource for breeding birds need to be clarified. In this study Blue Tits (\(Cyanistes\) \(caeruleus\)) and Great Tits (\(Parus\) \(major\)) were provided with supplementary food to investigate whether food availability reduced the costs of breeding for adults, and affected life history traits. Food supplementation with peanut cake disrupted the timing of Great Tit breeding and reduced fecundity. There was no effect of food supplementation on Great Tit adult or juvenile survival, except in 2010 when females traded off fecundity against future survival. Blue Tit fecundity was largely unaffected by food supplementation, but the provision of mealworms improved adult female survival. Food supplementation reduced female Daily Energy Expenditure (DEE) for both species during egg laying and for Great Tits feeding nestlings, revealing unexpectedly complex life history strategies. Through the integration of physiological techniques and life history frameworks we can understand the interaction between organisms and their environment and the effects of anthropogenic actions such as food supplementation of birds.