Complex Timing of Marsh Harrier Circus aeruginosus Migration Due to Pre- and Post-Migratory Movements

[摘要] Wetrackedthreejuvenileand14adultMarshHarriersCircusaeruginosusfromsouthernSwedenviasatellitetoinvestigatemigrationstrategies.Fourindividualsweretrackedforatleasttwoyears.Allthreejuvenilesandfouroftheadultsmadewest-orientedpre-migratorymovementswellbeforetheonsetofautumnmigration,andtrans-Saharanmigrantsvisitedpost-migratorystopoverareasintropicalAfrica.Bythesemovements,theharrierspresumablyexploitshort-termregionalvariationinfoodabundance.Autumnandspringmigrationoccurredinarelativelynarrowcorridor,withoutdistinctdifferencesbetweensexesintiming,speed,distance,anddurationofmigration,exceptthatfemalestendedtomigratefasterinspringthandidmales.Juvenilesmigratedshorterdistancesthanadults,andmigrationspeedswerelower.Springmigrationwassimilartoautumnmigrationintermsofspeedandduration.JuvenilesdidnotcrosstheSaharaDesertandthreebirds,onefemaleandtwojuveniles,winteredinEurope,whichisinaccordancewitharecentincreaseinthenumberof(juvenile)MarshHarrierswinteringinnorthwesternEurope.AllbirdsthatcrossedtheSaharawinteredintropicalWestAfrica.Harriersshowedsitefidelitytobreeding,winteringandstopoverareas.TheoverallmigrationspeedofMarshHarrierswassimilartothatofOspreysPandionhaliaetusandHoneyBuzzardsPernisapivorus,twoothertrans-Saharanmigrants.Ospreysusefly-and-foragemigrationtopromoteresultingspeed,whereasHoneyBuzzardsareparticularlyapttoexploitthermalsoaring.HowMarshHarriersbalanceforagingversustravellingtoaccomplishtheirrapidmigrationspeedsremainstoberesolved.

[学科分类] 动物科学

[关键词] Marsh Harrier