title: Life-history characteristics influence physiological strategies to cope with hypoxia in Himalayan birds.
abstract: Hypobaric hypoxia at high elevation represents an important physiological stressor for montane organisms, but optimal physiological strategies to cope with hypoxia may vary among species with different life histories. Montane birds exhibit a range of migration patterns; elevational migrants breed at high elevations but winter at low elevations or migrate further south, while high-elevation residents inhabit the same elevation throughout the year. Optimal physiological strategies to cope with hypoxia might therefore differ between species that exhibit these two migratory patterns, because they differ in the amount time spent at high elevation. We examined physiological parameters associated with blood-oxygen transport (haemoglobin concentration and haematocrit, i.e. the proportion of red blood cells in blood) in nine species of elevational migrants and six species of high-elevation residents that were sampled along a 2200 m (1000-3200 m) elevational gradient. Haemoglobin concentration increased with elevation within species regardless of migratory strategy, but it was only significantly correlated with haematocrit in elevational migrants. Surprisingly, haemoglobin concentration was not correlated with haematocrit in high-elevation residents, and these species exhibited higher mean cellular haemoglobin concentration than elevational migrants. Thus, alternative physiological strategies to regulate haemoglobin concentration and blood O2carrying capacity appear to differ among birds with different annual elevational movement patterns.
authors.affiliation: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, USA sahasbarve@gmail.com.|Wildlife Institute of India, Chandrabani, Uttarakhand, India.
authors.forename: S
authors.identifier: 0000-0001-5840-8023
authors.initials: S
authors.lastname: Barve
authors.affiliation: Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, USA.
authors.forename: A A
authors.initials: AA
authors.lastname: Dhondt
authors.affiliation: Wildlife Institute of India, Chandrabani, Uttarakhand, India.
authors.forename: V B
authors.initials: VB
authors.lastname: Mathur
authors.affiliation: Division of Biological Sciences, University of Montana, Missoula, MT, USA.
authors.forename: Z A
authors.initials: ZA
authors.lastname: Cheviron
mesh_terms: D000531:Altitude; D025041:Animal Migration; D000818:Animals; D006400:Hematocrit; D000860:Hypoxia; D007194:India; D010100:Oxygen / Q000097:blood; D046109:Passeriformes / Q000097:blood* / Q000502:physiology*; D012621:Seasons
chemical_list: D010100:Oxygen
keywords: Himalayas; birds; comparative physiology; elevational migration; haematocrit; haemoglobin concentration