Trophic behavior and parasite communities in kelp gulls from the northern Patagonian coast, Argentina.

Parasites are important components of biodiversity and play multiple roles in natural systems. In aquatic birds, endoparasites are acquired mainly through the diet; thus, the environment is the main determinant of the parasitic community. The kelp gull is a widespread, generalist and opportunistic seabird species. Owing to their feeding plasticity, the aim of this study was to analyse the composition and structure of the helminth community of two kelp gull groups on the northern Patagonian coast: one group pecked on the backs of southern right whales, whereas the other fed on fishing discards. These results were compared with those of a previous study in which a kelp gull group fed on natural prey items in Península Valdés. Among the 95 analysed gulls, 92.6% were parasitized by at least one helminth species, including Cestoda, Trematoda, Nematoda and Acanthocephala, with trematodes being the most diverse. The pecking of gulls on whale backs resulted in a more depauperate parasitic community. The parasitological results suggest that altered feeding behavior in kelp gulls reduces natural prey consumption, emphasizing the importance of parasites as integral components of biodiversity and trophic markers. It also highlights the urgent need to manage urban waste and fishery discards on the northern Patagonian coast to reduce kelp gull-whale interactions.