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Marine Ecology Progress Series

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MEPS 660:189-201 (2021)  -  DOI:

The importance of marine resources in the diet of urban gulls

Joana Pais de Faria1,#,*, Patrícia T. Vaz1,#, Catarina S. Lopes1, Joana G. Calado1,2,3, Jorge M. Pereira1,4, Sara N. Veríssimo1, Vitor H. Paiva1, Ana M. M. Gonçalves1,5, Jaime A. Ramos1

1University of Coimbra, MARE - Marine and Environmental Sciences Centre, Department of Life Sciences, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal
2Molecular and Environmental Biology Centre (CBMA), Universidade do Minho Campus de Gualtar, 4710-057 Braga, Portugal
3Animal Ecology Group, Universidade de Vigo, Lab 97, Torre CACTI, Campus As Lagoas, 36310 Vigo, Spain
4Environment and Sustainability Institute, University of Exeter, Penryn Campus, Penryn TR10 9FE, UK
5Department of Biology and CESAM, University of Aveiro, 3810-193 Aveiro, Portugal
#These authors contributed equally to this work
*Corresponding author:

ABSTRACT: The availability of anthropogenic food subsidies has promoted an increase in generalist opportunistic gull species, which currently breed and forage on predictable anthropogenic resources (e.g. landfills). Here we investigated whether marine resources are still important to urban-dwelling gulls. We studied 4 natural and 2 urban yellow-legged gull Larus michahellis colonies and compared (1) diet composition (through pellet analysis) and (2) isotopic niches of adults and chicks, (3) diet delivered to chicks of different ages, and (4) fatty acid (FA) composition of fledglings, in order to assess diet composition, diversity and quality, and the relevance of marine prey for natural and urban gull populations. Adult urban gulls consumed considerably lower proportions of marine prey when compared to gulls from natural colonies; however, they fed their younger chicks (<20 d old) mostly with fish, representing 61-80% of their chick food deliveries. Refuse items were mostly delivered to chicks older than 20 d. Overall, urban isotopic niches were not completely distinct from those of natural colonies, in some cases sharing ca. 50% of their niche space. Fledglings from the most urbanized colony presented overall higher FA concentrations and diversity, but they were lacking some omega-3 FAs relevant to their physiology. Our results highlight the importance of marine resources in the diet of urban gulls, particularly during early chick rearing, the relevance of food sources in the area around the breeding colonies and the fact that urban gulls benefit from year-round reliable anthropogenic food resources.

KEY WORDS: Urban gulls · Yellow-legged gull · Larus michahellis · Diet · Trophic ecology · Isotopic niches · Fatty acid composition

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Cite this article as: Pais de Faria J, Vaz PT, Lopes CS, Calado JG and others (2021) The importance of marine resources in the diet of urban gulls. Mar Ecol Prog Ser 660:189-201.

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