Meeting Abstract

70.2  Wednesday, Jan. 6  Scaling of escape flight performance, power output, and muscle function in perching birds JACKSON, B.E.; The University of Montana, Missoula brandon.jackson@mso.umt.edu

Patterns of scaling in animal locomotion offer insight to physical constraints imposed on evolution. Flight, being metabolically costly yet evolutionarily successful, is a particularly useful locomotor behavior through which to examine effects of scaling on locomotor performance, behavior, and ecology. Order Passeriformes (perching birds) includes ~50% of extant avian species, and a diverse array of ecologies, making them a critical component to our understanding of scaling in birds. I used a phylogenetically controlled 3-D kinematic analysis of 32 species of passerines (5 – 900 g) performing maximal escape takeoff and vertical flight. Body mass (M_b) specific climb power output scaled as M_b^-0.17, controlling for typical foraging location (ground vs. elevated). Total mass specific power output estimated from aerodynamic models scaled as M_b^-0.10, and was limited by a ceiling that scaled approximately as M_b^-0.2. Ground foraging species performed significantly better than elevated foragers, and resident species performed marginally better than long-distance migrants. Ground foragers also had relatively shorter wings, higher wingbeat frequencies, and greater hind-limb contribution to takeoff. In a complementary study I measured in vivo muscle function using sono-strain surgical implants in a single passerine clade, Corvidae (Gray Jay, Black-billed Magpie, American Crow, and Common Raven). Muscle mass (M_m) specific mechanical power output scaled as M_m^-0.2. In both muscle output and whole-body performance, wingbeat frequency appears to impose an ultimate limit. However, the positive allometry of muscle strain (M_b^0.11) and wing size (length: M_b^0.41) are potential compensatory mechanisms reducing the effects of body size on whole-body performance via wingbeat frequency. Funded by NSF IBN-0417176.