title: The roller coaster flight strategy of bar-headed geese conserves energy during Himalayan migrations.
abstract: The physiological and biomechanical requirements of flight at high altitude have been the subject of much interest. Here, we uncover a steep relation between heart rate and wingbeat frequency (raised to the exponent 3.5) and estimated metabolic power and wingbeat frequency (exponent 7) of migratory bar-headed geese. Flight costs increase more rapidly than anticipated as air density declines, which overturns prevailing expectations that this species should maintain high-altitude flight when traversing the Himalayas. Instead, a "roller coaster" strategy, of tracking the underlying terrain and discarding large altitude gains only to recoup them later in the flight with occasional benefits from orographic lift, is shown to be energetically advantageous for flights over the Himalayas.
authors.affiliation: School of Biological Sciences, Bangor University, Bangor, Gwynedd, UK.
authors.forename: C M
authors.initials: CM
authors.lastname: Bishop
authors.affiliation: School of Biological Sciences, Bangor University, Bangor, Gwynedd, UK.
authors.forename: R J
authors.initials: RJ
authors.lastname: Spivey
authors.affiliation: School of Biological Sciences, Bangor University, Bangor, Gwynedd, UK. c.bishop@bangor.ac.uk l.hawkes@exeter.ac.uk.
authors.forename: L A
authors.initials: LA
authors.lastname: Hawkes
authors.affiliation: Wildlife Science and Conservation Center of Mongolia, Ulaanbataar, Mongolia.
authors.forename: N
authors.initials: N
authors.lastname: Batbayar
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: B
authors.initials: B
authors.lastname: Chua
authors.affiliation: Office of the Dean of Graduate Research, University of Tasmania, Tasmania, Australia.
authors.forename: P B
authors.initials: PB
authors.lastname: Frappell
authors.affiliation: Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: W K
authors.initials: WK
authors.lastname: Milsom
authors.affiliation: Mongolian Academy of Sciences, Ulaanbataar, Mongolia.
authors.forename: T
authors.initials: T
authors.lastname: Natsagdorj
authors.affiliation: Emergency Prevention System(EMPRES) Wildlife and Ecology Unit, Food and Agriculture Organization of the United Nations (FAO), Rome, Italy.
authors.forename: S H
authors.initials: SH
authors.lastname: Newman
authors.affiliation: Department of Biology, McMaster University, Ontario, Ontario, Canada.
authors.forename: G R
authors.initials: GR
authors.lastname: Scott
authors.affiliation: San Francisco Bay Estuary Field Station, Western Ecological Research Center, U.S. Geological Survey, Vallejo, CA 94592 USA.
authors.forename: J Y
authors.initials: JY
authors.lastname: Takekawa
authors.affiliation: Max Planck Institüt für Ornithologie, Radolfzell, Germany. Department of Biology, University of Konstanz, Konstanz, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Wikelski
authors.affiliation: School of Biosciences, University of Birmingham, Birmingham, UK.
authors.forename: P J
authors.initials: PJ
authors.lastname: Butler
mesh_terms: D000531:Altitude; D025041:Animal Migration; D000818:Animals; D001696:Biomechanical Phenomena; D001831:Body Temperature; D001835:Body Weight; D004734:Energy Metabolism; D005426:Flight, Animal / Q000502:physiology*; D005777:Geese / Q000502:physiology*; D006339:Heart Rate; D018609:Tibet; D014921:Wings, Animal / Q000502:physiology*