Foraging ecology and dive behaviour of Pitt Island shags (Stictocarbo featherstoni) | Notornis and Birds New Zealand

Southern Bird

Bell, M¹ 

关键词: dive depth;    dive duration;    foraging ecology;    Pitt Island shag;    Stictocarbo featherstoni;   

DOI  :  

学科分类：农业科学（综合）

来源: Ornithological Society of New Zealand Inc.

【 摘 要 】

TheforagingecologyofPittIslandshag(Stictocarbofeatherstoni)wasstudiedusingGPSarchivalandTimeDepthRecorderdevicesdeployedonincubatingbirds.PittIslandshagsforagedexclusivelyduringdaylight,withatendencyformalestoforagemainlyduringmid-morningandlateafternoon,andfemalesintheearlymorningandaroundmid-day.Meanforagingdistancefromcolonieswas5.2km(range0.4-18.2km),withmales(mean9.7km)foragingsignificantlyfurtherthanfemales(3.7km).Bothsexesshowedhighforagingsitefidelity.Thedepthofmost(83%)divesgt;5mdeepweresimilartothedepthoftheprecedingdive(within30%),indicatingthatbirdsarealmostexclusivelybenthicfeedingwiththesmallfluctuationsindivedepthlikelyreflectingchangesinseafloortopography.Meandivedepthwas6.6m,withmaximumdepth24.4m,although90%ofalldiveswereshallowerthan13mdeep.Meandivedurationwas22s,withamaximumof69s,althoughover90%ofdiveswereshorterthan40s.Therewasapositiverelationshipbetweendivedurationanddivedepth,wheredeeperdiveshadlongerduration.Meanrestperiodwas19swithaweakpositiverelationshipbetweenrestperiodanddurationoftheprecedingdive.Meanpercentagetimeunderwaterduringeachforagingtripwas50.1%,indicatingrelativelyhighforagingefficiency.Favouredforaginglocationsinshallowinshorewatersislikelytobearesponsebybirdsselectivelyforaginginshelteredwatersprotectedfromoceanicswells.Thismaybeafactorinfluencingpopulationdeclinesasitintensifiesrisktobirdsaspotentialthreatsmaybemoreconcentratedintheseareas.

【 授权许可】

Unknown