Alternative strategies in avian scavengers: how subordinate species foil the despotic distribution
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Trade-offs in species’ traits can mediate competition and enable coexistence. A key challenge in ecology is understanding the role of species’ trade-offs in maintaining diversity, and evolutionary trade-offs between the abilities of competing species are best understood by considering how competitive advantages change along an environmental gradient. Previous studies of such trade-offs are generally limited to two-species systems and a single trade-off. In this study, I consider the effect of trade-offs in search efficiency and competitive abilities on habitat use patterns among a diverse avian scavenger guild. I hypothesize that species’ dominance status and search efficiency will both be correlated with patch quality. Using counts of searching birds in areas that vary in habitat quality in terms of both wildlife and human settlement density and observations at experimental carcasses, I assess the competitive ability, search efficiency, and habitat use of seven avian scavenger species in Masai Mara National Reserve, Kenya. Findings support the hypothesis with Bateleurs, a species with high search efficiency, and Ruppell’s, Lappet-faced, and White-backed vultures, species with high individual or social dominance, preferentially exploiting habitats of high quality, while Tawny eagles and Hooded vultures, species with low search efficiency and competitive ability, prefer habitats of low quality. This paper demonstrates the importance of considering multiple strategies for assessing the effect of competition on habitat use within complex communities.
KeywordsInterspecific competition Dominance Habitat use Producer–scrounger Vultures
Research was conducted in collaboration with The Peregrine Fund’s Pan African Raptor Conservation Program. Funding for this study was provided by Princeton University, via the Pompeo M. Maresi Memorial Fund, Hawk Mountain Sanctuary, The Peregrine Fund, and The Explorer’s Club. Advice and comments from Keith Bildstein and my advisor, Daniel Rubenstein, and committee members—Andy Dobson, Henry Horn, Simon Levin, Munir Virani, and David Wilcove—were incredibly helpful as was the statistical support of Charles Yackulic. Field assistance was provided by Wilson and Jon Masek. I would like to thank Narok County Council, the staff of Masai Mara National Reserve, particularly Mr. Minis and Mr. Sindiyo for their assistance and permission to conduct this research as well as the neighboring group ranches and conservancies and Africa Eco-Camps for their support. I’m thankful to Kenya Wildlife Service and the National Museums of Kenya.
Experiments conducted as part of this study comply with Kenyan laws and were covered under research permit NCST/5/002/R/448.
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