Show simple item record

dc.contributor.advisorWilkins, R. Neal
dc.contributor.advisorHejl, Sallie
dc.creatorJuarez Berrios, Edwin Alfredo
dc.date.accessioned2005-02-17T21:06:02Z
dc.date.available2005-02-17T21:06:02Z
dc.date.created2004-12
dc.date.issued2005-02-17
dc.identifier.urihttp://hdl.handle.net/1969.1/1574
dc.description.abstractOver the past 100–150 years Texas rangelands have dramatically changed from native open savannahs to dense woodlands. On the Edwards plateau, a major management concern is the increasing encroachment of Ashe juniper (Juniperus ashei). Preceding an anticipated brush management program, I investigated the presence, co-occurrence, and habitat relationships of 7 breeding bird species in the Leon River Watershed in central Texas, USA: black-capped vireo (Vireo atricapillus), golden-cheeked warbler (Dendroica chrysoparia), northern bobwhite (Colinus virginianus), white-eyed vireo (Vireo griseus), Bell’s vireo (Vireo bellii), painted bunting (Passerina ciris), and brown-headed cowbird (Molothrus ater). Vegetation characteristics were compared between sites occupied by each species and unoccupied sites using univariate analysis. Models for predicting species site occupancy were developed (using logistic regression) based on habitat characteristics correlated with the presence of each species. Two species of special concern, the endangered black-capped vireo and golden-cheeked warbler occupied 5.6% of sites and 13.8% of sites respectively, while the brood parasite brown-headed cowbird was the most widespread, occupying 86.8% of sites. Species co-occurrence patterns revealed significant associations between the golden-cheeked warbler and each of 5 other species. For most species, variables included in habitat models could be explained by knowledge of species known habitat associations. For example, the black-capped vireo was positively associated with increasing low-growing (<1.5 m) hardwood cover and with Low Stony Hill ecological sites. The golden-cheeked warbler was positively associated with increasing density of larger juniper trees, increasing variability in vertical vegetation structure, and decreasing midstory canopy of deciduous nonoaks (e.g., cedar elm [Ulmus crasifolia]). It also preferred Low Stony Hill and Steep Adobe ecological sites. Site occupancy seemed to be driven by variables that describe overall vegetation structure. In particular, cover of low-growing non-juniper vegetation and juniper tree density appeared to be important in determining site occupancy for several species. Although the models constructed were not very robust, resource managers can still benefit from such models because they provide a preliminary examination of important controlling variables. Managing rangelands to maintain or restore a mosaic of juniper patches and open shrublands are likely to help meet the habitat requirements of these bird communities.en
dc.format.extent1633306 bytesen
dc.format.mediumelectronicen
dc.format.mimetypeapplication/pdf
dc.language.isoen_US
dc.publisherTexas A&M University
dc.subjectAshe juniperen
dc.subjectblack-capped vireoen
dc.subjectbrush managementen
dc.subjectco-occurrenceen
dc.subjectDendroica chrysopariaen
dc.subjectecological siteen
dc.subjectendangered speciesen
dc.subjectgolden-cheeked warbleren
dc.subjecthabitat relationshipsen
dc.subjectJuniperus asheien
dc.subjectLeon River Watersheden
dc.subjectmicrositesen
dc.subjectlogistic regressionen
dc.subjectsite occupancyen
dc.subjectVireo atricapillusen
dc.subjectrangelandsen
dc.subjectTexasen
dc.titleHabitat relationships of seven breeding bird species in the Leon River Watershed investigated at local scalesen
dc.typeBooken
dc.typeThesisen
thesis.degree.departmentWildlife and Fisheries Sciencesen
thesis.degree.disciplineWildlife and Fisheries Sciencesen
thesis.degree.grantorTexas A&M Universityen
thesis.degree.nameMaster of Scienceen
thesis.degree.levelMastersen
dc.contributor.committeeMemberSmeins, Fred
dc.type.genreElectronic Thesisen
dc.type.materialtexten
dc.format.digitalOriginborn digitalen


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record