Both diet and exercise training are associated with muscle performance and endurance. Migratory birds undergo intense endurance exercise. In fact, a recent review indicated that flapping flight costs more energy (9 x increase from basal metabolic rate) than required by elite athletes competing in the Tour de France (4.3 x increase from basal metabolic rate) (Butler, 2016). Unlike running animals, migratory birds fuel endurance exercise with fats as opposed to carbohydrates. It is perhaps not surprising, therefore, that the main flight muscle (pectoralis) of migratory birds increases in size and ability to take up fats for metabolism during migration. Similarly, the liver of these birds also nearly doubles in size and increases the ability to create fats in preparation for migration as well as handle the breakdown of fats to fuel migration.
A new study of European starlings (Sturnus vulgaris), published in the American Journal of Physiology – Regulatory, Integrative and Comparative Physiology, examined how endurance flight training and diet impact gene expression in the pectoralis muscle and liver. What they found was that flight training in a wind tunnel increased several genes associated with fat metabolism and uptake in the muscle of the birds as well as one gene responsible for breaking down fats in the liver. Similarly, a diet containing higher amounts of poly unsaturated fatty acids (PUFAs) also increased the expression of a gene associated with the breakdown of fats in the muscle of the flight-trained birds.
PJ Butler. The physiological basis of bird flight. Philosophical Transactions of the Royal Society B – Biological Sciences. 371(1704): 2016.
KJ DeMoranville, WA Carter, BJ Pierce, SR McWilliams. Flight training in a migratory bird drives metabolic gene expression in the flight muscle but not liver, and dietary fat quality influences select genes. American Journal of Physiology – Regulatory, Integrative and Comparative Physiology, 319(6): R637-652,2020.