P2.112 Thursday, Jan. 5 Does the energetically expensive lifestyle of swallows affect thermogenic capacity? ZHANG, Y.*; SWANSON, D.L.; Univ. of South Dakota email@example.com
Because both summit (Msum = maximum thermoregulatory metabolic rate) and maximum (MMR = maximum exercise metabolic rate) metabolic rates are functions of skeletal muscle metabolism, correlations between these measures of maximal metabolic output could occur, but this has been little studied in birds. Moreover, because energetically expensive lifestyles are often correlated with high metabolic rates, cross-training effects of a high-energy lifestyle (i.e., high exercise) on thermogenesis, and vice versa, may exist. We tested this cross-training hypothesis with swallows, a family with an energetically expensive aerial insectivore lifestyle. Specifically, we measured basal and summit metabolic rates in six species of temperate-zone breeding swallows to address the question of whether a high-exercise lifestylewas reflected by elevated BMR and thermogenic capacity. BMR for temperate-zone swallows was higher than for tropical swallows, similar to results from other bird taxa. In addition, our preliminary data suggest that BMR in swallows shows a tendency to be higher than BMR for other birds. In contrast, Msum values for the species of swallows that we measured were consistent with Msum values for other swallow species, including tropical species, but the Msum-mass regression for swallows was not significantly different from the Msum-mass regression for other birds. These data suggest that swallow Msum is similar to that for other birds so cross-training effects are not apparent.Thus, the energetically expensive lifestyle of swallows apparently elevates maintenance energy expenditure, but not thermogenic capacity.