Meeting Abstract

20.1  Friday, Jan. 4  Metabolic Power, Mechanical Efficiency, and Heat Production during Hovering and Forward Flight in Calliope Hummingbirds (Selasphorus calliope) POWERS, D.R.*; TOBALSKE, B.W.; George Fox University, Newberg, OR; University of Montana, Missoula, MT dpowers@georgefox.edu

Flight requires higher power output than other forms of animal locomotion, and the effects flight speed upon power have important implications for the ecology and evolution of different flight styles. We studied the conversion efficiency of metabolic power (MBP) produced during hovering and forward flight in calliope hummingbirds (Selasphorus calliope; ~2.5 g) to mechanical power (MEP) production by the pectoralis muscle. Measurements were made in a wind tunnel at speeds ranging from 0-12 m/s. To determine MBP we measured oxygen consumption using negative-pressure, open-flow respirometry. To measure MEP we used stereo particle image velocimetry (PIV). We sampled the wake along planar, parasagittal transects separated by 1 cm, then integrated velocity with respect to area to obtain total kinetic energy flux within one wingbeat. Because mechanical efficiency (MEF) is low we accounted for the balance of MBP, most of which is released as heat, using infrared thermography to calculate heat dissipation from the general body surfaces. MBP exhibited a typical U-shaped curve. MEF for hovering and 10 m/s was ~8%, similar to previously reported values. MEF at 2-8 m/s was only ~4%, this might be an underestimate arising from the complexity of the aerodynamic wake at intermediate flight speeds. Heat dissipation exhibits strong negative correlation with wind speed (R2 range 0.75-0.93) but does not correlate with calculated MEF further highlighting that our estimates of efficiency at intermediate speeds might be underestimated. Funded by NSF IOS-0923606 & IOS-0919799, NASA 10-BIOCLIM10-0094, the Richter Scholar Program (GFU), and FLIR Systems, Inc.