Habitat relationships of seven breeding bird species in the Leon River Watershed investigated at local scales

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Title: Habitat relationships of seven breeding bird species in the Leon River Watershed investigated at local scales
Author: Juarez Berrios, Edwin Alfredo
Abstract: Over 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 .
URI: http : / /hdl .handle .net /1969 .1 /1574
Date: 2005-02-17

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Habitat relationships of seven breeding bird species in the Leon River Watershed investigated at local scales. Available electronically from http : / /hdl .handle .net /1969 .1 /1574 .

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