Breeding Season Home Range and Habitat Use of Mexican Spotted Owls (Strix occidentalis lucida) Below the South Rim of Grand Canyon National Park
2015
Bowden, Tim S. | Ferguson, Jake M. | Ward, Rolla V. | Taper, Mark L. | Willey, David W.
We studied breeding season home range characteristics and habitat of paired male Mexican Spotted Owls (Strix occidentalis lucida) below the south rim of Grand Canyon National Park from 2004–2005. Adult male owls (n = 5) were captured and radio-tracked using tail-mounted VHF transmitters. We used minimum convex polygons and 90% fixed kernels to estimate breeding season home range size (mean = 355 ha and 372 ha, respectively). We also generated adaptive kernel home range estimates to describe areas of concentrated use within home ranges. Home ranges were located in the upper reaches of relatively narrow rocky canyons, and Spotted Owls showed limited use of adjacent forested plateaus. We conducted an analysis of habitat use and selection at two scales and found that owls selected (i.e., used disproportionate to availability) limestone cliffs present in their home ranges. Home ranges were approximately centered on nest and associated roost sites located on limestone cliffs within canyons. Our results contrasted with observations in Utah where spotted owls nested primarily on sandstone cliffs. In Grand Canyon, both sandstone and limestone cliffs were present in the home range, but limestone appeared to be the preferred substrate. At the landscape level, owls placed home ranges in areas dominated by piñon-juniper (Pinus edulis – Juniperus monosperma) woodland. We delineated 40 ha use-areas around nest sites and found that these conservation zones closely approximated adaptive kernel 30% isopleths, thus supporting core area designation of the Mexican Spotted Owl Recovery Plan.
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