Endurance flight of migratory birds is an extraordinary physical performance carried out at a very high metabolic rate, which is about twice the maximum rate of exercising small mammals. Moreover, this high metabolic rate is maintained during non-stop flights of up to 200 h in certain species and while fasting. With the exception of aerial feeders, migrants do not feed during endurance flight and, thus, have to rely exclusively on body stores for energy and water. Endurance flight of birds is performed at 60–85% maximal oxygen uptake or more when birds are loaded with fuel. A prolonged exercise, such as a long flight accomplished during migration, involves a rise in the metabolic rate compared to the levels of an animal at rest. Moreover, the depletion of the available fuel accumulated in pre-migratory phase leads to the production of metabolites that can cause serious damage to the body of the animal, such as reactive oxygen species (ROS), which can damage the DNA. Intense and prolonged physical activity is normally associated with an increased production of ROS and thus the risk of oxidative stress. In pigeons, a long flight causes an increase of ROMs and a simultaneous decrease in antioxidant capacity. However, data on oxidative stress and DNA damage marker in birds undergoing endurance flights is very limited. In migratory birds, the level of oxidative stress decreases with time spent at stopover site, but how this happens is not well known. Adjusting the rest/activity patterns could be a strategy use to cope with migratory stress, as well as the diet could have an effect on the oxidative stress. The main aims of the project are: To discover whether migratory birds arriving to a stopover site after a long migratory flight have elevated markers of oxidative stress (ROS, Oxidation products) and of DNA damage that correlate to depletion of fat stores; To study if the patterns of rest and activity across the 24 hr depends on the condition at arrival and are functional to reduce levels of oxidative stress and DNA damage as shown by Total Antioxidative Capacity and DNA repair enzymes; To test if refuelling after a long fast (as experienced during the migratory flight) results in a reduction of oxidative stress and DNA damage.
Interdisciplinary Research Network Grant, Faculty of Life Sciences, University of Vienna