Combination of at-sea activity, geolocation and feather stable isotopes documents where and when seabirds molt

Yves Cherel (1) , Petra Quillfeldt , Karine Delord (1) , Henri Weimerskirch (1)

1 CEBC - Centre d'Études Biologiques de Chizé - UMR 7372

Keyfacetsoftheforagingecologyofseabirdsduringtheinter-breedingperiodstillremainpoorlyunderstoodbecauseofthedifficultyofstudyingthematsea,includingduringtheenergy-demandingmoltingstage.Here,theextenttowhichthreesympatricpetrels(Antarcticandthin-billedprions,andbluepetrel)fromthesubantarcticKerguelenIslandsmodifytheirforagingecologyduringmoltwasinvestigatedusingacombinationofcomplementarytools,namelyminiaturizedsaltwaterimmersiongeolocators(GLS)andtheisotopicmethod.Firstly,moltingbehaviorwasfirstcharacterizedinthebluepetrel,areferencespeciesthatisknowntorenewitsplumageinautumn.GLSandfeatherstableisotopes(13dCasaproxyofthebirds’foraginghabitat)indicatedthatthepost-breedingmoltofbluepetreloccurredinAntarcticwaters.Importantly,activityrecordersshowedthatmoltwasmarkedbyastrongpeakintimespentdailysittingonwater,whichthereafterdeclinedtolowervaluesduringtheremainingwintermonths.Secondly,thepeakintimespentsittingonwaterwasusedasaproxytocharacterizethecontrastedmoltstrategiesofthetwoprionspecies.Asbluepetrelsdemonstrated,thin-billedprionsmoltedduringthepost-breedingperiodincoldAntarcticwaterswheretheyfedprimarilyonlowtrophiclevelprey,mostlikelyAntarctickrill(15dNasaproxyofthebirds’diet).Bycontrast,Antarcticprionspresentedanunexpectedpre-breedingmoltoflongerdurationthattookplacefurthernorth,inwarmsubtropicalwaters.Interestingly,thetwoAntarcticmoltingspecies,thebluepetrelandthin-billedprion,renewedtheirplumageatthesametimeandwithinthesameoceaniczonethatislikelytobeapreviouslyundescribedhotspotofseabirddiversitydurintheAustralautumn.Thestudycontributestoagrowingbodyofevidencethatclosely-relatedspeciesexhibitvariousforagingstrategiesallowingecologicalsegregationandshedsnewlightonthepoorlyknowncriticalmoltingstagefseabirds.

Mots clés: body feathers; flight feathers; inter-breeding period; petrels; Procellariiformes; Southern Ocean; winter

Domaines: Sciences de l'environnement

Yves Cherel, Petra Quillfeldt, Karine Delord, Henri Weimerskirch. Combination of at-sea activity, geolocation and feather stable isotopes documents where and when seabirds molt. Frontiers in Ecology and Evolution, 2016, 4 (3), pp.1-16. ⟨10.3389/fevo.2016.00003⟩. ⟨hal-01291355⟩