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.

Further observations and implications of Oil Palm Elaesis guineensis fruit consumption by Hooded Vultures Necrosyrtes monachus in coastal Gambia.

“…Despite being widely distributed in sub-Saharan Africa, the Hooded Vulture has suffered severe population declines across the entire range and is currently listed as Critically Endangered by the IUCN (BirdLife International 2017). Highly commensal West African birds differ considerably in feeding behaviour and in general ecology from their East and southern African conspecifics, although more research is needed in this area (Barlow et al 2020). There are also huge variations in home ranges between regional populations as proven by satellite tracking studies (Reading et al 2019, Thompson et al 2020.…”

More resourceful scavenging by opportunistic Hooded Vultures Necrosyrtes monachus in coastal Gambia with photographic proof of tongue use when foraging for live food and blood.

“…However, recent work supports the widely held opinion past and present that N. monachus is monotypic. This is based on the homogeneity of a wide-ranging set of morphometric measurements and a constancy of plumage characteristics across the entire range (Barlow et al 2020, Mundy 2020. These studies conclude that detectable variation in size (particularly wing length) across the western, eastern and southern populations is clinal and that the recognition of N. m. pileatus cannot be justified.…”