Homogeneity in cranial biometrics and bill morphology is verified by measurements from The Gambia, Botswana and Kenya in the case of the putative sub-species of the highly commensal Hooded Vulture Necrosyrtes monachus monachus and non-commensal Necrosyrte

Abstract

We present biometrical data assembled from a combined total of 37 complete and partially cleaned skulls and feathered heads for the two putative subspecies of Hooded Vulture Necrosyrtes monachus monachus and N. m. pileatus (which Mundy et al. (1992) credibly argue should be N. m. carunculatus). We report on mostly insignificant variation in measurements taken from across three regions of the Hooded Vulture range. For N. m. pileatus (n = 22) the measurements are assembled from 13 live birds captured, tagged and released in Botswana between 2014-2017, seven museum specimens held in The National Museums of Kenya collected during 1913-1950, and two as described below. We compare with N. m. monachus (n = 14) where we measured eight specimens produced by road traffic accidents in The Gambia 2002-2019 of which seven are cleaned bare skulls and one a feathered study skin. We also measured six feathered heads and three skulls from several different countries in Africa, collected during 1832-1929 (n = 6 monachus, 2 pileatus, and 1 unknown) and held at the Natural History Museum, Tring, UK. Cranial materials for Hooded Vulture are scarce in world museums and the Gambian sample consisting of seven cleaned skulls represents the largest known number for a single country. Different populations across the regions vary considerably in both feeding habits and home ranges. We hypothesised that different foraging ecologies may have led to adaptation in bill morphology. Presented here for the first time are a series of skull morphometrics which test for variation in cranial biometrics and bill morphology from across the range of the Hooded Vulture. The Gambian bird has been DNA sequenced and a planned genetics study of other populations will resolve the long-standing taxonomic debate.