Flight costs and fuel composition of a bird migrating in a wind tunnel

We studied the energy and protein balance of a Thrush Nightingale Luscinia luscinia, a small long-distance migrant, during repeated 12-hr long Eights in a wind tunnel and during subsequent two-day fueling periods. From the en ergy budgets we estimated the power requirements for migratory flight in th is 26 g bird at 1.91 Watts. This is low compared to flight cost estimates i n birds of similar mass and with similar wing shape. This suggests that pow er requirements for migratory flight are lower than the power requirements for nonmigratory Eight. From excreta production during Right, and nitrogen and energy balance during subsequent fueling, the dry protein proportion of stores was estimated to be around 10%. A net catabolism of protein during migratory flight along with that of fat may reflect a physiologically inevi table process, a means of providing extra water to counteract dehydration, a production of uric acid for anti-oxidative purposes, and adaptive changes in the size of Eight muscles and digestive organs in the exercising animal .