Energy management strategies and tradeoffs throughout the annual and life cycle

Many birds that breed in southern Sweden stay year-round, enduring the harsh winter instead of migrating. They experience immense temperature, daylight, and resource fluctuations throughout the year. Their energy budget is split between different needs such as feeding chicks, shivering to staying warm, and the minimum energy needed to maintain vital body functions and the immune system (basal metabolism, or BMR). The relationships between different metabolic rates and their underlying mechanisms are poorly understood, but the few previous studies suggest that portions of the energy budget can enhance or trade-off with one-another. For example, shivering to staying warm may drive up energy costs for basic bodily functions like maintaining skeletal muscles and organs in the respiratory and digestive system. On the other hand, intense exercise (for example, flying and feeding chicks) may trade-off with basal metabolism if there is not enough energy to cover both, or to prevent overheating. If different types of work relate differently to BMR, this would indicate a trade-off between investing in winter survival or reproduction. My goal is to find out if birds that spend the winter in cold climates have different metabolic strategies that favor either winter survival or breeding success. I will also identify and test potential mechanisms for observed patterns. As we are facing climate change, these questions may be important for understanding how birds respond and potentially evolve with warmer temperatures and more frequent extreme weather.

I will use a combination of lab studies and field studies with both captive birds (zebra finches) and wild birds (blue tits). I will make use of the respirometry equipment in the wind tunnel to measure metabolic rates during different activities. Birds that use nest boxes in the Revinge area will be used for experiments and subsequently monitored during the breeding season. Zebra finches from the captive colony at Stensoffa will be used in exercise-training experiments. The combination of experimental and observational approaches, using both wild and captive models will enhance our understanding of the patterns and processes underlying metabolic strategies.