title: Energy Expenditure and Metabolic Changes of Free-Flying Migrating Northern Bald Ibis.
abstract: Many migrating birds undertake extraordinary long flights. How birds are able to perform such endurance flights of over 100-hour durations is still poorly understood. We examined energy expenditure and physiological changes in Northern Bald Ibis Geronticus eremite during natural flights using birds trained to follow an ultra-light aircraft. Because these birds were tame, with foster parents, we were able to bleed them immediately prior to and after each flight. Flight duration was experimentally designed ranging between one and almost four hours continuous flights. Energy expenditure during flight was estimated using doubly-labelled-water while physiological properties were assessed through blood chemistry including plasma metabolites, enzymes, electrolytes, blood gases, and reactive oxygen compounds. Instantaneous energy expenditure decreased with flight duration, and the birds appeared to balance aerobic and anaerobic metabolism, using fat, carbohydrate and protein as fuel. This made flight both economic and tolerable. The observed effects resemble classical exercise adaptations that can limit duration of exercise while reducing energetic output. There were also in-flight benefits that enable power output variation from cruising to manoeuvring. These adaptations share characteristics with physiological processes that have facilitated other athletic feats in nature and might enable the extraordinary long flights of migratory birds as well.
authors.affiliation: Institute of Avian Research "Vogelwarte Helgoland", An der Vogelwarte 21, 26386, Wilhelmshaven, Germany.
authors.forename: Franz
authors.initials: F
authors.lastname: Bairlein
authors.affiliation: Center for Organismic Systems Biology, Departments of Anthropology and Behavioral Biology, University of Vienna, Althanstr. 14, 1090, Vienna, Austria; Waldrappteam, Schulgasse 28, 6162 Mutters, Austria, and Konrad-Lorenz Research Station, 4645, Grünau, Austria.
authors.forename: Johannes
authors.initials: J
authors.lastname: Fritz
authors.affiliation: Clinic for Avian, Reptile, and Fish Medicine, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1210, Wien, Austria.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Scope
authors.affiliation: Central Laboratory, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1210, Wien, Austria.
authors.forename: Ilse
authors.initials: I
authors.lastname: Schwendenwein
authors.affiliation: Clinic for Avian, Reptile, and Fish Medicine, University of Veterinary Medicine Vienna, Veterinärplatz 1, 1210, Wien, Austria.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Stanclova
authors.affiliation: Center for Behavior and Neurosciences (CBN), Rijksuniversiteit Groningen, Nijenborgh 7, 9747, AG, Groningen, The Netherlands; Centrum voor Isotopen Onderzoek (CIO), Rijksuniversiteit Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands.
authors.forename: Gertjan
authors.initials: G
authors.lastname: van Dijk
authors.affiliation: Centrum voor Isotopen Onderzoek (CIO), Rijksuniversiteit Groningen, Nijenborgh 4, 9747, AG, Groningen, The Netherlands.
authors.forename: Harro A J
authors.initials: HA
authors.lastname: Meijer
authors.affiliation: Center for Behavior and Neurosciences (CBN), Rijksuniversiteit Groningen, Nijenborgh 7, 9747, AG, Groningen, The Netherlands.
authors.forename: Simon
authors.initials: S
authors.lastname: Verhulst
authors.affiliation: Center for Organismic Systems Biology, Departments of Anthropology and Behavioral Biology, University of Vienna, Althanstr. 14, 1090, Vienna, Austria.
authors.forename: John
authors.initials: J
authors.lastname: Dittami
mesh_terms: D000222:Adaptation, Physiological; D000273:Adipose Tissue / Q000378:metabolism; D000693:Anaerobiosis; D025041:Animal Migration; D000818:Animals; D001717:Birds / Q000097:blood / Q000378:metabolism* / Q000502:physiology; D001784:Blood Gas Analysis; D004573:Electrolytes / Q000097:blood; D004734:Energy Metabolism; D005426:Flight, Animal; D006003:Glycogen / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D004573:Electrolytes; D017382:Reactive Oxygen Species; D006003:Glycogen