Evidence of niche differentiation for two sympatric vulture species in the Southeastern United States

Amanda E Holland,James C Beasley,Jeffrey Hepinstall-Cymerman,Olin E Rhodes,Travis L Devault,Michael E Byrne,A Lawrence Bryan

doi:10.1186/s40462-019-0179-z

Abstract

BackgroundAs obligate scavengers utilizing similar habitats, interspecific competition undoubtedly occurs between resident black (Coragyps atratus) and turkey (Cathartes aura) vultures. In the interest of exploring how sympatric species coexist through habitat segregation, we examined resource selection of resident black and turkey vultures in the southeastern United States (US) for evidence of niche differentiation.MethodsUsing fine-scale movement data, we assessed interspecific seasonal differences in monthly roost reuse frequency and roost site fidelity, as well as monthly flight, roost, and diurnal rest site resource selection based on > 2.8 million locations of 9 black vultures and 9 turkey vultures tracked from September 2013 to August 2015 using Groupe Spécial Mobile/Global Positioning System (GSM/GPS) transmitters.ResultsBlack vultures generally exhibited greater roost fidelity as well as a greater maximum number of nights spent at a single roost than turkey vultures. Patterns of flight, roost, and resting habitat selection within the home range varied monthly as well as between species, providing evidence for habitat segregation and niche differentiation by sympatric vultures. In particular, our results indicate the importance of wooded wetlands for resting and roosting locations for both species, and revealed clear differences in the use of forested habitats between species during flight, resting, and roosting behavioral states.ConclusionsBy examining differences in resource selection and spatial ecology of black and turkey vultures across a range of behaviors, this study demonstrates mechanisms of niche differentiation in these ecologically similar species, and enhances potential for conservation and informed management of this important group of birds.

Highlights

Competition between sympatric resident, non-migratory species occurs throughout the annual cycle when resource requirements are similar; niche differentiation reduces competition and allows for resource partitioning and coexistence [1,2,3]
Twenty-seven vultures (13 black vultures – 5 males and 4 females, and 14 turkey vultures – 6 males and 3 females) were trapped, tagged, and affixed with Groupe Spécial Mobile (GSM)/ Global Positioning System (GPS) tracking devices resulting in 2,823,627 locations collected among all vultures from 13 June 2013 to 31 August 2015
After excluding data collected from vultures whose movement did not span a full month and months wherein vultures exhibited migratory movements, we estimated 322 monthly 100% home ranges from 9 black vultures and 9 turkey vultures (n = 150 and 170, respectively)

Summary

Introduction

Competition between sympatric resident, non-migratory species occurs throughout the annual cycle when resource requirements are similar; niche differentiation reduces competition and allows for resource partitioning and coexistence [1,2,3]. Interspecific competition undoubtedly occurs between black and turkey vultures as both species are diurnal, obligate scavengers utilizing similar roosting [12,13,14] and nesting habitats [15, 16]. Black vultures have a minimal sense of smell, forage with conspecifics, maintain large social groups, and respond to visual cues of other scavenging birds for improved carcass detection [16, 17]. As obligate scavengers utilizing similar habitats, interspecific competition undoubtedly occurs between resident black (Coragyps atratus) and turkey (Cathartes aura) vultures. In the interest of exploring how sympatric species coexist through habitat segregation, we examined resource selection of resident black and turkey vultures in the southeastern United States (US) for evidence of niche differentiation

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