Flying high: limits to flight performance by sparrows on the Qinghai-Tibet Plateau.
Limits to flight performance at high altitude potentially reflect variable constraints deriving from the simultaneous challenges of hypobaric, hypodense and cold air. Differences in flight-related morphology and maximum lifting capacity have been well characterized for different hummingbird species across elevational gradients, but relevant within-species variation has not yet been identified in any bird species. Here we evaluate load-lifting capacity for Eurasian tree sparrow (Passer montanus) populations at three different elevations in China, and correlate maximum lifted loads with relevant anatomical features including wing shape, wing size, and heart and lung masses. Sparrows were heavier and possessed more rounded and longer wings at higher elevations; relative heart and lung masses were also greater with altitude, although relative flight muscle mass remained constant. By contrast, maximum lifting capacity relative to body weight declined over the same elevational range, while the effective wing loading in flight (i.e. the ratio of body weight and maximum lifted weight to total wing area) remained constant, suggesting aerodynamic constraints on performance in parallel with enhanced heart and lung masses to offset hypoxic challenge. Mechanical limits to take-off performance may thus be exacerbated at higher elevations, which may in turn result in behavioral differences in escape responses among populations.
Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Sciences, Hebei Normal University, Shijiazhuang 050024, People's Republic of China.|Ocean College, Agricultural University of Hebei, Qinhuangdao 066003, People's Republic of China.
Yan-Feng
YF
Sun
Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Sciences, Hebei Normal University, Shijiazhuang 050024, People's Republic of China.
Zhi-Peng
ZP
Ren
Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Sciences, Hebei Normal University, Shijiazhuang 050024, People's Republic of China.
Yue-Feng
YF
Wu
Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, People's Republic of China.
Fu-Min
FM
Lei
Department of Integrative Biology, University of California, Berkeley, Berkeley, CA 94720, USA wings@berkeley.edu lidongming@hebtu.edu.cn.
Robert
R
Dudley
Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Sciences, Hebei Normal University, Shijiazhuang 050024, People's Republic of China wings@berkeley.edu lidongming@hebtu.edu.cn.
Dong-Ming
0000-0003-2759-3435
DM
Li
D000531:Altitude; D000818:Animals; D017753:Ecosystem; D005260:Female; D005426:Flight, Animal / Q000502:physiology*; D006321:Heart / Q000502:physiology; D008168:Lung / Q000502:physiology; D008297:Male; D009132:Muscles / Q000502:physiology; D046370:Sparrows / Q000033:anatomy & histology / Q000502:physiology*; D018609:Tibet
Altitude; Eurasian tree sparrow; Flight; Maximum performance; Wing loading