Geometric morphometric analysis of the humerus in New and Old World vultures

Abstract

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

Carrion converging: Skull shape predicts feeding ecology in vultures

“…The description ‘low and slender’ is commonly used to differentiate all vultures, accipitrids included, from non‐scavenging raptors (Guangdi et al., 2015; Hertel, 1994; Pecsics et al., 2019), underscoring the importance of describing feeding ecology in finer detail. Some distinguishing features of the accipitrid skull could offer advantages in the predominantly open, grassland habitats of these vultures (Holmes et al., 2022). Accipitrid vultures tend to soar at higher altitudes and consume larger carcasses than cathartids (Houston, 1984; Mundy et al., 1992), relying primarily on vision to locate both conspecifics and carcasses (Dermody et al., 2011; Potier, 2020).…”

“…Across the 23 extant species, vultures exhibit phylogenetic (Jarvis et al., 2014), ecological (Linde‐Medina et al., 2021; van Overveld et al., 2020), and morphological diversity (Böhmer et al., 2020; Hertel, 1994; Holmes et al., 2022). Distinctions in sociality (Kendall, 2013; van Overveld et al., 2020), breeding and nesting behavior (Kemp & Kemp, 1975; Kendall, 2013; Krüger et al., 2015; Mundy et al., 1992), migratory and movement patterns (Alarcón & Lambertucci, 2018), habitat preferences (del Hoyo et al., 1992; Kendall, 2014), sensory perception (Jackson et al., 2020; Ogada et al., 2012; Portugal et al., 2017; Spiegel et al., 2013), and feeding and foraging strategies (Houston, 1987; Jackson et al., 2020; Kruuk, 1967; Ogada et al., 2012; van Overveld et al., 2022) have been recorded.…”

Carrion converging: Skull shape is predicted by feeding ecology in vultures

“…The description "low and slender" is commonly used to differentiate all vultures, accipitrids included, from non-scavenging raptors (Hertel, 1994;Guangdi et al, 2015;Pecsics et al, 2019), underscoring the importance of describing feeding ecology in finer detail. Some distinguishing features of the accipitrid skull could offer advantages in the predominantly open, grassland habitats of these vultures (Holmes et al, 2022). Accipitrid vultures tend to soar at higher altitudes and consume larger carcasses than cathartids (Mundy et al, 1992;Houston, 1984), relying primarily on vision to locate both conspecifics and carcasses (Dermody et al, 2011;Potier, 2020).…”

“…Across the 23 extant species, this guild exhibits phylogenetic (Jarvis et al, 2014), ecological (van Overveld et al, 2020Linde-Medina et al, 2021), and morphological diversity (Hertel, 1994;Böhmer et al, 2020;Holmes et al, 2022). Distinctions in sociality (Kendall, 2013;van Overveld et al, 2020), breeding and nesting behavior (Kemp & Kemp, 1975;Krüger et al, 2015;Kendall, 2013;Mundy et al, 1992), migratory and movement patterns (Alarcón & Lambertucci, 2018), habitat preferences (Kendall, 2014;Del Hoyo et al, 1992), sensory perception (Spiegel et al, 2013;Portugal et al, 2017;Ogada et al, 2012;Jackson et al, 2020), and feeding and foraging strategies (Kruuk, 1967;Houston, 1987;Ogada et al, 2012;Jackson et al, 2020;van Overveld et al, 2022) have been recorded.…”