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Flight Morphology, Energetic Condition, and the Stopover Biology of Migrating Thrushes
Wang Yong and Frank R. Moore
Vol. 111, No. 3 (Jul., 1994), pp. 683-692
Published by: American Ornithological Society
Stable URL: http://www.jstor.org/stable/4088471
Page Count: 10
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Flight morphology affects aerodynamic performance and the energetic demand for migration. We investigated the relationship between flight morphology and energetic condition of Wood Thrush (Hylocichla mustelina), Veery (Catharus fuscescens), Swainson's Thrush (C. ustulatus), and Gray-cheeked Thrush (C. minimus) during migration and the consequences for stopover behavior following spring trans-Gulf passage. Differences in morphological variables were found among Catharus thrushes, and between Wood Thrush and Catharus thrushes. Species with longer migratory distances have longer, more pointed wings and higher aspect ratios. The relatively larger wing area and lower body mass of Gray-cheeked Thrush and Veery result in lower wing loadings. Whereas wing size increased with increasing lean body mass in all species, the interrelations of wing span and wing area with lean body mass were allometrical (i.e. deviated from expected isometric relationship). Larger individuals in each species have disproportionately large wings. Wing size was negatively related to amount of stored fat, which indicated that larger individuals within each species have smaller fat stores remaining after trans-Gulf migration. Species or individuals with relatively long, pointed wings are more efficient migrants, and their energetic demand per unit distance travelled is lower. The consequences vis-a-vis stopover biology are considered.
The Auk © 1994 American Ornithologists' Union