Meeting Abstract
P1.52 Thursday, Jan. 3 The Effect of Some Physiological, Morphological, and Environmental Variables on Hovering Metabolic Rate in Hummingbirds POWERS, DR*; SMITH, KM; WETHINGTON, SM; GETSINGER, PW; TOBALSKE, BW; George Fox University, Newberg, OR; George Fox University, Newberg, OR; Hummingbird Monitoring Network, Patagonia, AZ; George Fox University, Newberg, OR; University of Portland, Portland, OR dpowers@georgefox.edu
We measured hovering metabolic rate (HMR) during nectar feeding under varying temperature and wind conditions in 7 hummingbird species with body sizes ranging from 3-8 g. Whole-animal HMR was positively correlated with body mass (slope = 0.4, R2 = 0.72) while mass-specific HMR did not change notably with body mass (slope = -0.05, R2 = 0.38) averaging around 0.6 mL O2 g-1min-1. For 3 species ranging in mass from 3-8 g mass-specific HMR appears to be positively correlated with wing loading (slope=0.22, R2=0.88) but shows no relationship with wingspan (slope=-0.01). We had sufficient data to analyze temperature and wind effects on HMR in 5 species. Overall we found little evidence for thermoregulatory substitution using heat produced during hovering at operative temperatures between 15-45 �C. HMR increased with temperature in 3 species with temperature explaining as much as 26% of the variation and suggesting increased thermoregulatory cost. No wind effects were observed between 0-2.5 m/s, but this could change when wind-direction data are included in the analysis.
