Abstract
Our understanding of the adaptive control of the timing and intensity of reproduction in birds is largely built on knowledge on selection pressures acting in the egg laying and the nestling phase. Accumulation of data for the incubation phase has recently shown that parental energy expenditure during incubation is as costly as during the nestling period. Since an incubating bird experiences a strong reduction in available foraging time, and food availability is often low, incubation may also exert an important selection pressure on reproduction. In this project we will study the mechanism and the function of incubation behavior in the great tit, with the aim to integrate this knowledge in our understanding of the adaptive control of the timing and intensity of reproduction. The approach is to link behavioral decisions on a short time base to the time budget, the energy balance and fitness consequences. We will 1) experimentally determine the effect of thermal environment, clutch size, food availability and male feeding on the time and energy budget of the incubating bird, 2) experimentally quantify the effect of incubation on both parental and clutch fitness, 3) develop a model to predict the optimal timing and intensity of egg care for known temperature and food availability regimes and 4) test this model with data on both actual incubation patterns in the study population and the timing of incubation in a latitudinal range of other great tit populations. To achieve this goal we will use automatic registration of incubation rhythms, and estimate the energetic cost of incubation both using measurements of oxygen consumption, doubly labeled water and a heated artificial brood patch. Experimental manipulation of the thermal environment, food availability, male assistance and clutch size will quantify behavioral responses of the birds and enable us to estimate the subsequent fitness consequences.
Netherlands