Connectivity and Age Distribution of the Baltic Common Guillemot Uria aalge Population: Evidence from Morphometry and Ringing Recoveries

摘要

Inevolutionaryecology,environmentalmonitoringandconservationmanagement,reliableinformationonphenotypicanddemographictraitsinmarineseabirdsishighlywanted,butdifficulttoacquire.Therefore,freshlydeadCommonGuillemotsUriaaalge(n=149)incidentallydrownedinsalmondriftgillnetsintheBalticSea,duringOctobera€”November,werestudied.Wenotedage,sex,moultpatternandfatstatus,andtookmorphometricmeasurementstocomparewithdatafromtheNortheastAtlanticpopulation.Onlyminorphenotypicdifferenceswerefound.Thebirdshadslightlylongerwingsthanexpectedatthelatitudewheretheywerecollected,probablyduetotheirnewlygrownprimariesand/orobserverdifferences,ratherthanageneticdivergence.TheBalticGuillemotappearsnottobeadistinctsubspecies,butonlythemarginalmemberofademe.RingingrecoveriesalsosuggestintermittentexchangeofbirdsbetweentheBalticandtheNorthSea.Youngbirdsdidnotseemtobeover-representedingillnetbycatches.Ourfoundagedistributiona€”withaheavydominanceofadultbirds,butfewimmature/juvenilesa€”deviatedfromthatreportedearlier,andsuggeststhatthepopulationismorevulnerabletoadultmortalitythroughbycatchingillnetsthanpreviouslybelieved.