Theses and Dissertations at Montana State University (MSU)
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Item Mexican Spotted Owl reproduction, home range, and habitat associations in Grand Canyon National Park(Montana State University - Bozeman, College of Letters & Science, 2008) Bowden, Timothy Scott; Chairperson, Graduate Committee: Mark L. Taper; David Willey (co-chair)Mexican spotted owls (Strix occidentalis lucida) are nocturnal avian predators that are widely distributed in the southwest U.S. and northern Mexico. In 1993, the lucida subspecies was listed as threatened in response to concern over the loss of forest habitats to which the owl is widely associated. However, in the northwestern corner of their range spotted owls primarily inhabit steep-walled rocky canyons. Owl populations inhabiting this region have received less attention than populations using forests, although, canyon populations are important to the persistence of the subspecies, and are subject to different environmental pressures. I investigated the breeding ecology and home range characteristics of Mexican spotted owls within Grand Canyon which supports both forest and rocky canyon habitat. During the study from 2004 - 2006, female fecundity (mean = 0.86), calculated as the number of female fledglings per paired female, was relatively high compared to values reported previously for Mexican spotted owls. Five adult male owls were radio-tracked during the breeding season. I used minimum convex polygons and fixed kernel estimates to describe home range size (mean = 356 ha and 372 ha, respectively) and generated adaptive kernels to describe areas of concentrated use within home ranges. I used GIS to describe vegetation and geology cover types associated with owl use areas. This information was used to determine if spotted owls used landscape cover types disproportionately to their availability. At a landscape level, spotted owl telemetry locations were positively correlated with piñyon-juniper vegetation that occurred within canyons as well as with the Redwall and Muav geologic layers (pItem Exploring relationships among recreation, habitat type, and Mexican spotted owls on the Colorado Plateau in Southern Utah(Montana State University - Bozeman, College of Letters & Science, 2011) Hockenbary, Chad Evan; Chairperson, Graduate Committee: David WilleyThe Mexican spotted owl (Strix occidentalis lucida) was listed as "threatened" in 1993 by the U.S. Fish and Wildlife Service. In Utah, the spotted owl is associated with rocky canyons that attract high levels of human recreation. Recreation could potentially have negative effects on the owl. I investigated roost behavior, territorial occupancy rates, and reproduction in canyon habitats that differed in recreation level and habitat condition (e.g., xeric versus mesic environments). Surveys were conducted in four areas in Utah: Zion and Capitol Reef National Parks, Grand Staircase-Escalante National Monument, and the Cedar Mesa-Elk Ridge highland. In Chapter 2, I evaluated possible differences in behaviors by fledglings across different levels of recreation. Fledgling diurnal behaviors were dependent on recreation level (P < 0.05). Fledglings in both recreation classes spent approximately = 50% of their time roosting, but fledglings associated with high-recreation territories spent more time in maintenance behaviors (13% vs. 4%) and less time in vigilant behaviors (29% vs. 35%) than did those in low-recreation territories. In Chapter 3, results from a top-ranked regression model indicated potential association between owl site occupancy rates and habitat type, with mesic sites showing higher occupancy than xeric sites in 2008: 0.75 (95% CI = 0.57 - 0.87) and 0.50 (95% CI = 0.27 - 0.73). Recolonization rate was 0.53 (95% CI = 0.28 - 0.76) for mesic sites and 0.10 (95% CI = 0.02 - 0.37) for xeric sites. Extinction rate was constant across years and sites (0.25; 95% CI = 0.15 - 0.39). Detection probability was 0.89 (95% CI = 0.82 - 0.94) across all three years of study. The number of fledglings per pair was greater in 2009 (0.94) than 2008 (0.25) and 2010 (0.50). My results suggest that recreation could have altered diurnal roost behavior of fledglings but was not related to occupancy and reproduction of Mexican spotted owls.