Meeting Abstract

105.1  Wednesday, Jan. 7  Elevational variation in flight mechanics and energetics of the giant Andean hummingbird FERNANDEZ, Maria Jose*; DUDLEY, Robert ; Univ. of California, Berkeley; Univ. of California, Berkeley mjose@berkeley.edu

Hummingbirds are unique in their ability to sustain hovering, one of the most energetically demanding forms of locomotion. The giant hummingbird (Patagona gigas) weighs on average 20 g, twice as much as the second-largest hummingbird, making it an outlier in the hummingbird body size distribution. Despite the challenges of supporting its large body weight, P. gigas also inhabits a broad altitudinal range from sea level to 3,800 m in South America. At high elevations, the lower air density relative to sea level will reduce lift production, and mechanical power output must increase. At the same time, the lower partial pressure of oxygen may constrain metabolic power production. Thus, the occurrence of P. gigas at a wide range of altitudes provides an excellent natural experiment, and the opportunity to assess biomechanical and energetic responses of this bird to natural hypobaric conditions. The objectives of this study are to determine how P. gigas modulates kinematic and energetic parameters at high elevation in order to cope with enhanced energetic demands. Contrary to previous studies with small hummingbirds, we found that the giant hummingbird significantly increases both wing stroke amplitude and wingbeat frequency under hypobaria. Also, oxygen consumption during hovering increases significantly from sea level to 3,800 m.