Habitats Used Abundance And Distribution Of The Mexican Spotted Owl Strix Occidentalis Lucida On National Forest System Lands

I studied the habitat characteristics of Mexican Spotted Owls (Strix occidentalis lucida), a federally threatened species, in the Canyonlands region of southern Utah. Vegetative and geologic features were measured within 10m wide belt plots at each current or historic nest/roost site. Based on our findings, past research, and species life history characteristics, I constructed a species distribution model (SDM) predicting Mexican Spotted Owl distribution in Utah for the Colorado Plateau region. The SDM was generated using the following inputs as important habitat variables: elevation, aspect, surface ratio, curvature, slope, geology, and vegetation. Program R was used for model development and generation. The SDM was generated using an ensemble model approach by combining three modeling techniques: random forest, logistic regression, and maximum entropy. This study combines measured habitat characteristics, with sophisticated geographic information system (GIS) tools and SDMs to provide managers with an informative and useful toolkit for Mexican Spotted Owl conservation.

"In 1993 the U.S. Fish and Wildlife Service (FWS) listed the Mexican spotted owl (Strix occidentalis lucida; "owl") as threatened under the Endangered Species Act (ESA). Critical habitat for the Mexican spotted owl was designated in 2004, comprising approximately 3.5 million hectares (ha) (8.6 million acres [ac]) on Federal lands in Arizona, Colorado, New Mexico, and Utah (69 FR 53182). Within the critical habitat boundaries, critical habitat includes protected and restricted habitats as defined in the original Mexican Spotted Owl Recovery Plan, completed in 1995. The species' recovery priority number is 9C, pursuant to the Endangered and Threatened Species Listing and Recovery Priority Guidelines (48 FR 43098). The Mexican spotted owl meets the species recovery priority 9C category due to its moderate degree of threat, high recovery potential, taxonomic classification as a subspecies, and conflict with construction or other economic activities. Surveys since the 1995 Recovery Plan have increased our knowledge of owl distribution but not necessarily of owl abundance. An owl site is an area with a high probability of being used by a single or a pair of adult or subadult owls for nesting, roosting, or foraging. For the current revision, the Recovery Team compiled over 1,300 owl sites known today in the U.S. portion of the owl's range (Table II.1; Table B.1 in Appendix B). The increase in the number of owl sites is mainly a product of new surveys being completed within previously unsurveyed areas (e.g., several National Parks within southern Utah, Grand Canyon in Arizona, Guadalupe National Park in West Texas, Guadalupe Mountains in southeastern New Mexico and West Texas, Dinosaur National Monument in Colorado, and Cibola National Forest in New Mexico), with only a few additions to numbers of sites recorded for previously well-surveyed National Forests. Thus, an increase in abundance cannot be inferred from these data."

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