Recent, Rapid, Colonisation of Lao PDR from the South by Yellow-Vented Bulbul Pycnonotus Goiavier

摘要

Acrossmostofthetropicsitisoftendifficulttotellwhetherextensionsofknownrangebybirdspeciesreflectgenuinechangeorareartefactsofincreasedobservation.Yellow-ventedBulbulPycnonotusgoiavierisamainlySundaicpasserineknownfromsouthernIndochina(southernThailand,CambodiaandsouthernmostVietnam)formanydecades.ThefirstLaorecordcameonlyin1996butsincethenthespecieshasspreadnorththroughLaoPDRalongtheMekongandsomemajortributaries.AllLaorecordsarefromthelowlandplains,innon-foresthabitat.InspectionofthelocationsofrecordsandofbirdrecordingpatternsinLaoPDRovertimeindicatethatthisbulbul'snorthernexpansion,paralleledbyoneinadjacentThailand,issurelynotsimplythebelatedfindingofaspecieslong-overlooked.Bothclimatechangeandhabitatchange(forestconversionandfragmentation)areplausiblecauses.Thatfiveofsixnon-forestpasserinesthathavecolonised(ormassivelyexpandedin)LaoPDRinthelast30yearsarefromthesouth,withonefromthewestbutnonefromthenorth,maysuggestclimaticchangeasthecause,buttheirratesofexpansionfaroutstripnorthwardtemperaturemovement.WhileYellow-ventedBulbul'schangeinnationalstatusisobvious,eventhoughLaoPDRisoneoftheleastknowncountriesforbirdsinSouth-eastAsia,disentanglingtherolesofthesetwosimultaneousmajoreffectsinavifaunalchangeinSouth-eastAsiaischallenging.