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Title: Flights across the roof of the world
Author: Parr, N.
Awarding Body: University of Exeter
Current Institution: University of Exeter
Date of Award: 2020
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High-altitude environments present challenges to animal life, including cold temperatures, dehydration and reduced barometric pressure, resulting in diminished oxygen availability (hypoxia). Birds that migrate across high-altitude mountain ranges face these challenges whilst meeting the high metabolic demands of flight. In this thesis I develop scientific understanding of how avian migrants overcome this challenge and cross the Tibetan Plateau (the highest and largest land mass on Earth). Firstly, I consolidate research into the benefits that avian physiology can confer for funding high rates of metabolism at high altitude, relative to humans and other mammals. Secondly, I present empirical work that aims to investigate high-altitude flight during migration across the Tibetan Plateau, expanding the scientific literature that has previously focused on bar-headed geese (Anser indicus). I collate tracking data for nine species of birds that migrate across or around the Himalayas and Tibetan Plateau and investigate whether there are common techniques that reduce flight costs and minimise exposure to hypoxia. I also explore how thermoregulation in bar-headed geese may be affected by high altitude, using high resolution data collected during free flight over the Tibetan Plateau. Finally, I compare the muscular phenotype of high-altitude migrant ruddy shelduck (Tadorna ferruginea) and low-altitude congener, common shelduck (Tadorna tadorna), to investigate whether ruddy shelduck have physiological adaptations for flight at high altitude. The research carried out in this thesis reveals that i) multiple species reach altitudes in excess of 6,000 m whilst crossing the Tibetan Plateau, including cranes, raptors and waterfowl who’s flight altitudes have not been previously quantified; ii) with the exception of demoiselle cranes, most bird species reduce altitude exposure where possible; iii) bar-headed geese maintain core body temperatures within a relatively narrow range regardless of altitude, expanding our understanding of the high-altitude physiology of this iconic species; iv) ruddy shelduck may have adaptations to enhance the functional properties of mitochondrial enzymes, which may support high-altitude flight. Collectively, this work advances our knowledge of how migrants overcome the challenge of migration across high altitude through both physiological and behavioural adaptation and adjustment.
Supervisor: Hawkes, L. ; Bearhop, S. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available