Foraging movements of breeding Kelp Gulls in South Africa
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RESEARCH
Open Access
Foraging movements of breeding Kelp Gulls in South Africa Katharina Reusch1* , Nicolás Suárez2, Peter G. Ryan3 and Lorien Pichegru1,3
Abstract Background: Kelp Gulls Larus dominicanus are one of the most abundant gulls in the Southern Hemisphere and can play an important role in their ecosystem. Understanding their foraging ecology is therefore important, especially in the context of anthropogenic changes of the environment. Over 35,000 Kelp Gulls breed in South Africa but little is known about their habitat use. It has been hypothesised that foraging mainly occurs in natural habitats while provisioning chicks to ensure high quality food, but knowledge on their foraging ecology during the incubation period remains poor. Methods: We tracked incubating Kelp Gulls from six colonies distributed along the coast of South Africa, varying in their distance to urban areas and landfills, and compared foraging trip patterns and habitat selection between colonies. Results: Gulls from west coast colonies, generally located further from landfills than the other studied colonies, travelled farther from their breeding sites (11.7 ± 9.9–17.8 ± 21.7 km, n = 3 colonies) than birds from Cape Town and south and east coast colonies (1.7 ± 0.8–3.1 ± 3.7 km, n = 3) with birds travelling farthest when foraging at sea. Gulls from all colonies spent more time foraging in marine, coastal, and natural terrestrial environments than scavenging in strongly modified habitats while incubating. Conclusions: Our results suggest that Kelp Gulls in South Africa are able to exploit various resources from different foraging habitats, regardless of colony location and seem to rely less on anthropogenic habitats than expected. Keywords: Seabird ecology, Larus dominicanus, Bio-logging, Anthropogenic food
Background Humans are having increasingly profound impacts on the environment through a myriad of activities including urbanization, contributing towards global changes [1]. Some species show greater tolerance towards anthropogenic changes than others, for example by being less specialised in terms of habitat or diet and can benefit from altered conditions. Such species are considered ‘winners’ of global changes (e.g. [2]). By comparison, more specialised species with more sensitive requirements tend to be limited in their capacities to adapt to * Correspondence: [email protected] 1 Institute for Coastal and Marine Research, Department of Zoology, Nelson Mandela University, PO Box 77000, Port Elizabeth, South Africa Full list of author information is available at the end of the article
changes, and often experience population and range decreases as a result of global changes (e.g. [2–4]). Seabirds are particularly threatened by global changes with 28% of seabirds being categorised as either critically endangered, endangered or vulnerable [5]. As seabirds use both marine and terrestrial habitats ([5, 6]), threats include overfishing inducing depletion of their prey, bycatch in fisheries, pollution, introduced species in their
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