Foraging Habitat Selection in the Last Ortolan Bunting Emberiza hortulana Population in Switzerland: Final Lessons before Extinction

[摘要] TheOrtolanBuntingEmberizahortulanahassufferedageneraldeclineacrossmuchofWesternEuropeinrecentdecades.InSwitzerland,onlyonepopulationremainsinsub-Mediterraneanshrub-steppeonthesouth-facingslopesoftheRhôneValley(Valais).WeaimedtocollectdataonforagingecologyofthelastSwissOrtolanBuntingsduringreproduction.However,thispopulationunderwentaconsiderabledecline,withnobreedingconfirmedinSwitzerlandin2007.Weinvestigatedforaginghabitatselectionoffourunpairedmalesatthehabitatandmicrohabitatscales,andcomparedpatternsofforaginghabitatusewithpatternsofterrestrialinvertebrateabundance.Allradio-trackedbirdsforagedexclusivelyontheplain.Theadjacentslope,whichharbouredtheformerbreedinggrounds,wasusedonlyforterritorialsongdisplays.Allmalesshowedadisproportionateuseofconventionalmaizefieldsthathadbeentreatedwithherbicides,whilealsoexhibitinganavoidanceofmeadowsandriparianvegetation.Theseobservedpatternsofhabitatusemaybedrivenbyunavailabilityofoptimalforaginghabitat,withbirdsbeingforcedtousethebestofapoorsetofoptions.Structurally,itwasshownthatbirdsforagedinareaswithahighproportionofbareground,aswellasmoderatelydenseoverheadvegetation.Theseareasdidnotsupporthigherarthropodabundance,suggestingthatfoodaccessibility(and/orcover)ratherthanfoodabundancedictatedhabitatselection.ItremainstobeseenwhetherthesepatternsofmicrohabitatusealsoapplytobreedingOrtolanBuntings.FurtherworkinsouthernEuropeanbreedinggroundsshouldbeenvisionedtogaincrucialinformationabouttheecologicalrequirementsofOrtolanBuntingsinMediterraneanandsub-Mediterraneanhabitats.Additionally,effortneedstobefocusedonidentifyingfactorsaffectingthespeciesonthewinteringgrounds,whichmayassistinexplainingtheobserveddeclinesinthebreedingareas.

[学科分类] 动物科学

[关键词] Species Conservation