“The ecological physiology of lean mass dynamics during flight and refueling in migratory birds”

Dr. Alex Gerson
Professor, UMass Amherst
Department of Biology

During flight, fat is the primary fuel for endurance exercise, and protein is catabolized supplemental to fat, comprising only 5-15% of total energy expenditure. Due to this protein catabolism, long distance migrant birds arrive after flights with organ mass reductions as great as 50% of the pre-flight mass, yet are still able to refuel in preparation for the next leg of the journey. Although this phenomenon has been documented in many species of migratory bird, the physiological consequences of this degree of protein catabolism has not been studied.

This catabolism of protein results in the liberation of water, aiding in the maintenance of water balance, and results in greater mass loss, reducing the cost of flight. Thus, the costs of loss of function must be carefully balanced against the benefits of maintaining water balance and reducing flight costs.

I am currently evaluating the costs and benefits of organ and muscle catabolism using both field and laboratory based studies. In addition to providing insight into the physiological trade-offs experienced by these birds, these data will provide useful information to better understand lean mass recovery processes and impacts to physiological function.