Consumption of discards by Herring Gulls Larus argentatus and Lesser Black-backed Gulls Larus fuscus off the Belgian coast in the breeding season

Alejandro Sotillo, Jochen Depestele, Wouter Courtens, Magda Vincx, Eric Stienen

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    Fishery discards in the Belgian part of the North Sea are a source of food for
    Herring Gulls Larus argentatus and Lesser Black-backed Gulls L. fuscus. To
    understand the importance of discards for local L. argentatus and L. fuscus
    populations, single-item discard experiments were performed at four offshore
    distances from the gullery of the Port of Zeebrugge, at four different stages of
    the breeding season (May to August 2011). We compared flock composition
    during discarding with the distribution of Herring and Lesser Black-backed Gulls,
    with respect to offshore distance from the colony as reflected by an 11-year
    (2002–2013) dataset of standardised ship-based surveys. Consumption of
    discards depended on the type of fish that was discarded, but prey selectivity by
    adults was reduced during the chick rearing stage. A generalised linear mixed
    model identified the number of scavengers following the vessel, the proportion of
    adults and of Herring Gulls in the flock and the frequency of food robbery events
    interacting with the stage of the breeding season as affecting the variation in flatfish
    consumption. Shifts in scavenger flock composition and discard consumption
    between stages of the breeding season are likely linked to variation in food
    requirements of the gull population along the season and to dispersal patterns
    towards the end of summer. Nutrient requirements of breeding adults peak
    during the chick rearing stage, making this a key period in terms of dependence
    of the breeding parents on discarded fish as food source.
    Original languageEnglish
    Pages (from-to)195–205
    Number of pages10
    Publication statusPublished - 2014

    Thematic list

    • Fisheries (society)
    • Sea and coastal birds

    EWI Biomedical sciences

    • B280-animal-ecology

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