Habitat preferences of pinyon-juniper specialists near the limit of their geographic range

We investigated habitat preferences for five pinyon-juniper specialists dur ing the 1998 and 1999 breeding seasons in Utah juniper (Juniperus osteosper ma) woodlands of southwestern Wyoming. We compared avian use and availabili ty of vegetation features using univariate and multivariate analysis to det ect selection for vegetative features of pinyon-juniper specialists near th e northeastern range boundary of pinyon-juniper habitat on the Colorado Pla teau. Gray Flycatchers (Empidonax wrightii), Juniper Titmice (Baeolophus gr iseus), and Bewick's Wrens (Thryomanes bewickii) preferred woodlands with h igh overstory juniper cover. The Juniper Titmouse was associated with senes cent trees, Blue-frap Gnatcatcher (Polioptila caerulea) with rock outcrops and shrubs in the family Rosaceae, and Black-throated Gray Warbler (Dendroi ca nigrescens) with pinyon pine (Pinus edulis). We suggest the geographic d istribution of four of five pinyon-juniper specialists is limited by the oc currence of pinyon pine in semiarid woodlands on the northeastern Colorado Plateau. The geographic limit for Blue-gray Gnatcatchers in this region may correspond to the presence of mountain mahogany in the woodland understory . The conservation of pinyon-juniper specialists in southwestern Wyoming wi ll benefit from the maintenance of successional processes, particularly tho se that perpetuate mature woodlands with a pinyon pine component.