P1.217 Wednesday, Jan. 4 Heat Dissipation During Flight in Calliope Hummingbirds (Stellula calliope) MAKI, K.G.*; POWERS, D.R.; TOBALSKE, B.W.; George Fox Univ, Newberg, OR; George Fox Univ, Newberg, OR; University of Montana, Missoula, MT email@example.com
The energetic cost of flight in hummingbirds is among the highest transport costs measured and can exceed 10X BMR. Only ~10% of the energy expended during flight is converted to mechanical work with the balance converted to heat. While some of the heat produced by muscular activity during flight can be used in body-temperature maintenance much of it must be dissipated to avoid excessive hyperthermia. To gain a better understanding of heat dissipation from body surfaces during flight we used high-speed infrared video recordings (FLIR SC4000) to monitor changes in surface temperature of Calliope hummingbirds (Stellula calliope) during flight in a wind tunnel at speeds ranging from 0-12 m/s and correlated this with metabolic costs over the same range of flight speeds. Mean surface temperature decreased ~2 °C (25-23 °C ) over the range of flight speeds measured. Major regions of heat loss (MRHL) were the head, axillary region, breast, and legs. MRHLs exhibited surface temperatures 2-7 °C above mean surface temperature with the size of the head and axillary regions decreasing by 30-50% over the range of measured flight speeds. All MRHLs decreased by at least 2 °C between 0-12 m/s with head temperature decreasing by 4 °C. Our data suggest that excess heat during flight is dissipated primarily from the heat, axillary region, breast, and feet with heat being dissipated most rapidly from the head. The progressive reduction of mean surface temperature and surface temperature of MRHLs suggests that convective heat dissipation is an important mode of heat loss at higher flight speeds.