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In-flight turbulence benefits soaring birds

December 23, 2015

Birds use atmospheric updrafts to subsidize soaring flight. We observed highly variable soaring flight by Black Vultures (Coragyps atratus) and Turkey Vultures (Cathartes aura) in Virginia, USA, that was inconsistent with published descriptions of terrestrial avian flight. Birds engaging in this behavior regularly deviated vertically and horizontally from linear flight paths. We observed the soaring flight behavior of these 2 species to understand why they soar in this manner and when this behavior occurs. Vultures used this type of soaring mainly at low altitudes (<50 m), along forest edges, and when conditions were poor for thermal development. Because of the tortuous nature of this flight, we describe it as “contorted soaring.” The primary air movement suitable to subsidize flight at this altitude and under these atmospheric conditions is small-scale, shear-induced turbulence, which our results suggest can be an important resource for soaring birds because it permits continuous subsidized flight when other types of updraft are not available.

Publication Year 2016
Title In-flight turbulence benefits soaring birds
DOI 10.1642/AUK-15-114.1
Authors Julie M. Mallon, Keith L. Bildstein, Todd E. Katzner
Publication Type Article
Publication Subtype Journal Article
Series Title The Auk
Index ID 70160610
Record Source USGS Publications Warehouse
USGS Organization Forest and Rangeland Ecosystem Science Center