Factors affecting loggerhead shrike mortality in Virginia

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dc.contributor.authorBlumton, Arlene K.en
dc.contributor.committeechairFraser, James D.en
dc.contributor.committeememberKirkpatrick, Roy L.en
dc.contributor.committeememberStauffer, Dean F.en
dc.contributor.departmentFisheries and Wildlife Sciencesen
dc.date.accessioned2014-03-14T21:37:44Zen
dc.date.adate2012-06-10en
dc.date.available2014-03-14T21:37:44Zen
dc.date.issued1989-12-07en
dc.date.rdate2012-06-10en
dc.date.sdate2012-06-10en
dc.description.abstractI studied loggerhead shrikes (Lanius ludovicianus) in the Shenandoah Valley in Virginia from April 1987 to April 1988; factors affecting mortality rates wring the breeding season, fall dispersal, and winter were investigated., The high reproductive,success in this study was similar to that reported by other researchers in the United States. Reproductive success was different among varying grass heights and varying amounts of bare soil areas within 100 m of shrike nests; success was highest in habitats with numerous bare soil areas and medium grass. I radio-harnessed fledglings at a mean age of 56 days to document dispersal, fall home-range areas, and survival rates. During the postfledging dispersal period, survival rates were 100% fledglings dispersed at a minimum of 78 days of age, and fall home-ranges typically contained medium grass and numerous bare soil areas. These habitat characteristics may provide shrikes with increased invertebrate availability. Winter negatively affected the loggerhead shrike population in Virginia; raptor predation was the primary cause of subadult and adult mortality, and road kill was secondary. Shrikes moved from grassland areas to shrub-forest areas during inclement weather and preyed on small birds. Home-range sizes were larger during the winter than at other times of the year. I documented the occurrence of low levels of organochlorine and organophosphates in all birds analyzed for pesticide contamination. Also, I present statistical models to predict age and sex of loggerhead shrikes; wing chord and tail white on rectrix 5 were the most useful variables in discriminating sexes and wing chord was used in discriminating ages. More research is needed on the effects of raptors on shrike populations and on the role of foraging habitat on winter areas.en
dc.description.degreeMaster of Scienceen
dc.format.extentxii, 85 leavesen
dc.format.mediumBTDen
dc.format.mimetypeapplication/pdfen
dc.identifier.otheretd-06102012-040434en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-06102012-040434/en
dc.identifier.urihttp://hdl.handle.net/10919/43080en
dc.language.isoenen
dc.publisherVirginia Techen
dc.relation.haspartLD5655.V855_1989.B623.pdfen
dc.relation.isformatofOCLC# 21187069en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subject.lccLD5655.V855 1989.B623en
dc.subject.lcshLaniusen
dc.subject.lcshShrikesen
dc.titleFactors affecting loggerhead shrike mortality in Virginiaen
dc.typeThesisen
dc.type.dcmitypeTexten
thesis.degree.disciplineFisheries and Wildlife Sciencesen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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