Consumption of Discards by Herring Gulls Larus argentatus and Lesser Black-Backed Gulls Larus fuscus off the Belgian Coast in the Breeding Season

[摘要] FisherydiscardsintheBelgianpartoftheNorthSeaareasourceoffoodforHerringGullsLarusargentatusandLesserBlack-backedGullsL.fuscus.TounderstandtheimportanceofdiscardsforlocalL.argentatusandL.fuscuspopulations,single-itemdiscardexperimentswereperformedatfouroffshoredistancesfromthegulleryofthePortofZeebrugge,atfourdifferentstagesofthebreedingseason(MaytoAugust2011).WecomparedflockcompositionduringdiscardingwiththedistributionofHerringandLesserBlack-backedGulls,withrespecttooffshoredistancefromthecolonyasreflectedbyan11-year(2002–2013)datasetofstandardisedship-basedsurveys.Consumptionofdiscardsdependedonthetypeoffishthatwasdiscarded,butpreyselectivitybyadultswasreducedduringthechickrearingstage.Ageneralisedlinearmixedmodelidentifiedthenumberofscavengersfollowingthevessel,theproportionofadultsandofHerringGullsintheflockandthefrequencyoffoodrobberyeventsinteractingwiththestageofthebreedingseasonasaffectingthevariationinflatfishconsumption.Shiftsinscavengerflockcompositionanddiscardconsumptionbetweenstagesofthebreedingseasonarelikelylinkedtovariationinfoodrequirementsofthegullpopulationalongtheseasonandtodispersalpatternstowardstheendofsummer.Nutrientrequirementsofbreedingadultspeakduringthechickrearingstage,makingthisakeyperiodintermsofdependenceofthebreedingparentsondiscardedfishasfoodsource.

[学科分类] 动物科学

[关键词] Larus Fuscus