Staging Duration and Passage Population Size of Sanderlings in the Western Dutch Wadden Sea

[摘要] ThepopulationofSanderlingsCalidrisalbaalongtheEastAtlanticflywayhasgrownconsiderablyduringthelastdecades.Perhapsreflectingthisaugmentedpopulationsize,increasingnumbersofSanderlinghavebeenreportedtostageintheWaddenSeaduringspringandautumnmigration.EstimatesofthenumbersofSanderlingsintheWaddenSeahavepreviouslybeenbasedonalimitednumberofcountsthatwerenotcorrectedfortheturnoverofindividuals.Inthisstudy,weaccountedforturnoverusingestimatesoftheprobabilitythatindividuallycolour-ringedSanderlingsarestillpresenttwodaysafterasighting.Incombinationwithdailycountsduringhightide,weestimatedthetotalnumberofSanderlingsthatusedtheislandGriendandsurroundingmudflats,inthewesternDutchWaddenSea,duringsouthwardpassagein2013and2014.WealsoestimatedminimalstagingdurationsofSanderlingsatGriend.Non-moultingbirdsweresignificantlyheavieruponcapture,whichsuggeststhattheywererefuellingforlongnon-stopmigratoryflights.Wintersightingsconfirmedthatthenon-moultingSanderlingswinterinsub-SaharanAfricaandthatthemoultingSanderlingsspentthewinterinEuropeornorthernAfrica.WithanaverageminimalstayinthewesternDutchWaddenSeaof9daysin2013and12in2014,non-moultingSanderlingsstayedforamuchshortertimethanmoultingSanderlings,whichstayedfor32daysin2013and36daysin2014.Non-moultingindividualswerelesslikelytoberesightedbetweenyears.Estimatesofminimalstagingdurationarelikelyunderestimatesofthetruestagingduration,andweproposethatmoultingSanderlingsprobablycompletetheirwingmoultintheWaddenSea.WeestimatedthatthetotalnumberofSanderlingsusingthewesternDutchWaddenSeabeforemigrationtoEuropeanorAfricanwinteringareaswere27,546(95%Cl22,739–41,449)in2013and22,574(95%Cl16,436–46,114)in2014.Thiswouldamountto11–14%ofatotalflywaypopulationof200,000individuals,representinganamazingdegreeofconcentrationforwhatisregardedasaratherwidelyandthinlyspreadshorebirdspecies.

[学科分类] 动物科学

[关键词] Migration