Geometric Morphometric Analysis of the Humerus in New and Old world Vultures

The vulture guild is comprised of two distinct groups, Old and New World, that provide a unique insight into how morphology varies among convergent species. All vultures are considered to be large birds of prey that utilize a style of flight called thermal soaring to search and feed primarily on already dead animal flesh. Even though this flight style is exhibited among all 23 species, slight variations in their skeletal morphology may relate to their differences in ecology. I hypothesized that vulture humeral morphology varies in relation to these organisms' habitat, average body mass, courtship displays, and migration capabilities. To address this hypothesis, I used three-dimensional geometric morphometrics to measure the overall shape differences of vulture humeri. Computer models of each bone were created to observe the crucial skeletal features that relate to muscular functions and were analyzed using discriminant function analyses. Humeral morphology was found to vary most by habitat preference and body mass. Vultures that inhabit forested areas have humeri that exhibit features that suggest increased flapping flight compared to those in open and mountainous regions. The results for the heaviest species allude to these birds enhancing their wingbeats in ways other than humeral morphology