Nest-Site Selection and Nest Predation in the Great Bittern Botaurus stellaris Population in Eastern Poland

摘要

Thisstudyanalysestheeffectsofnest-siteselectiononpredationriskofGreatBitternBotaurusstellarisnests.ThestudywasconductedinfishpondsofeasternPolandduringfourbreedingseasons(2003a€“06).Thehabitatcharacteristicsof84nestsiteswereinvestigated.NestingsiteswerefoundwithinPhragmites,typha,CarexandScirpusvegetationinthereedbeltsurroundingthefishponds.Allnestswerebuiltatplaceshavingbetween10and97cmofwaterdepth.Predationwasthemajorcauseofnestfailureinthestudypopulation.However,norelationshipbetweennestsitevegetationtypeanddailynestsurvivalratewasfound.Thesurvivalofnestsatedgesandintheinteriorofreedbedswassimilar.AlogisticregressionmodelindicatedsignificanteffectsofwaterdepthandvegetationcoveronnestpredationintheBitternpopulation.Therewasatendencytowardsbettersuccessfornestsindenseemergentvegetationwithhigherwaterdepth.Theresultshaveimportantimplicationsforaneffectiveconservationstrategyforwetlandsholdinglargeandviablepopulationsofthisvulnerablespecies.