How Fledglings Explore Surroundings from Fledging to Dispersal. A Case Study with Eagle Owls Bubo bubo

摘要

Movementstrategiesareoneoftheprimarymechanismsunderlyinganimalsurvival.Despitetheimpressiveamountofstudiesonanimalmovementduringsuccessivestagesinthelifehistoryinbirds,littleisknownaboutthecharacteristicsofmovementsduringthepost-fledgingdependenceperiod.Suchaperiodrepresentsacrucialphaseofthelifehistoryduringwhichindividualscanshowimportantdisplacementsaroundthenatalnest.Merewepresentpathsearchstrategiesemployedbyradio-taggedfledglingEagleOwlsBubobuboduringthepost-fledgingdependenceperiod(1962locationsfrom41taggedowlets).Duringthepost-fledgingdependenceperiod,individualsshowdynamicmovementbehavioursthatmightberelatedtothedevelopmentofindividuals'mobilityandcognitiveabilities.Immediatelyafterleavingthenest,individualsfocusedtheiractivitiesclosetothenest,butafterafewweeksindividualstravelledfurtherandfaster,uptothemomentthattheystartedtodisperse.Atthetimethatthemobilityofowletswashighest,theirmovementsdescribedstraighterpaths,Movementpatternswerenotaffectedbymorphological-orphysiologicalparametersofbodycondition.Between-siblingdistancesshowedasignificantinteractionbetweensexandtime:until20daysafterowletsleftthenest,siblingswereclosertogether,independentlyofthesex.Between-siblingdistancesincreasedwithtimeasindividualsbecameincreasinglymobile;justbeforethestartofdispersal,familyunitsseemedtodissolve.