Untitled Energetics Bird migration typically consists of an alternation between flights, when distance is covered and energy consumed, and stopover periods when energy for the proceeding flights is accumulated. Consequently, fuel economy during both flight and stopover is of crucial importance for the birds' migration performance.
Birds show a variety of stopover and flight strategies.
Sometimes they migrate by numerous short flights and minimal energy reserves, and in other situations they build up large fuel loads and make long-distance flights. A primary objective in our research is to understand the major selection forces that govern the evolution of these different strategies. Predicted decision rules for the birds to adapt their departure fuel loads in relation to ,e.g., fuel deposition rate, are tested by field experiments. A key factor for the birds' optimal fuel reserves and for their resulting migration speed is the rate of fuel deposition at stopover sites. Nutrient and energy budget analyses in combination with respirometry are used to answer these and related questions.