Migration physiology and energetics of birds and bats

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Migratory birds and bats face extreme physiological challenges. Energy expenditure during flight is exceptionally high, and migrants sustain flight for many hours, days and even over a week without water, food or rest. They often fly at high altitudes in order to gain the assistance of tailwinds, forcing them to exercise intensely in thin air with low oxygen. When they stop to refuel they have high levels of activity, eating and digesting food. What migrants eat during refueling may be important for flight performance. In particular omega-3 fatty acids have been hypothesized to improve energy metabolism in shorebirds. Migrating bats and some birds (hummingbirds) use torpor (decreasing body temperature and metabolism to minimal levels) at stopovers to minimize the loss of fat during roosting periods when they are unable to feed. How torpor is switched on and off in these species is not known. The long term objective of my research is to understand the energetics and physiology of endurance flight and refueling of migratory birds and bats, and how these are affected by intrinsic factors (season, sex, age) and extrinsic conditions (altitude, temperature, humidity, diet, disease, and pollutants). In the short term we will study: 1) the physiological mechanisms that allow songbirds and shorebirds to fly at high altitudes; 2) energy costs and fuel substrate oxidation during flight using stable isotopes (13C enrichment) in breath; 3) the importance of biofilm feeding and omega-3 fatty acids for migration in shorebirds; 4) how the powerhouses of muscle cells (mitochondria) may be specialized for flight and torpor in migratory birds and bats; 5)the specialized physiology of ultra-endurance fliers. We will use specialized facilities and technologies for the proposed research. A unique hypobaric, climatic wind tunnel, specifically designed for birds, will be used to test the physiological effects of high altitude flight and energy costs in different species, sexes and ages. Carbon isotopes in breath will be measured in real time using a spectroscopic analyzer. Automated ground-based and satellite radio-telemetry will be used to track bird migrations after experimental manipulation of their diets. Mitochondrial function and free radicals that can damage cells during intense exercise will be measured by high-resolution respirometry. The research program will train 15 - 20 highly qualified personnel, advance basic knowledge, and have practical relevance for the conservation of migratory species. North American bird populations have declined by 30% since 1970, and Canada's long-distance migrants are at the greatest risk. Migratory bats are at elevated risk for mortality at wind energy developments, and they are very poorly studied. This research will improve our understanding of why these animals migrate the way they do, and thus help us protect them.