Graduation Date
Summer 2001
Document Type
Thesis
Program
Other
Program
Masters of Science
Committee Chair Name
Ralph J. Gutierrez
Committee Chair Affiliation
Cal Poly Humboldt Faculty or Staff
Second Committee Member Name
Mark A. Colwell
Third Committee Member Name
Judd A. Howell
Keywords
x
Abstract
I examined the distribution and habitat associations of northern spotted owls at the southern extent of their range in Marin County, California. To estimate density and distribution I used nighttime surveys followed by daytime visits to locate owls and estimate site occupancy status. I measured 26 macro and micro habitat variables at 46 occupied sites and compared them to an equal number of paired random sites. Spotted owls had a high density ( = 0.376 owls/ km), based on the 82 territorial owls found in the 218 km2 study area which is the greatest density yet reported for this species. The owl sites exhibited a random distribution pattern with the nearest neighbor distance between roosts averaging 1.48 km. Using a matched pair multiple logistic regression I found northern spotted ow] roost sites were more closely associated with greater diameter variance of trees, greater number of potential nest trees, and greater percents of slope, large downed woody material, and inorganic l itter at the microsite level than paired random sites (R2 = 0.983). At the landscape level spotted owls were more often found on the lower third of slopes Cx2 = 7.73, = 0.021), and roost stands typically had a single canopy species composition (x2 = 5.43, P < 0.001). Occupied sites also tended to have denser stands of larger conifers, whereas random sites tended to have more hardwoods. I also measured 28 nests and found that most nests were a platfonn type and located in a large conifer (n = 25 conifers, 3 hardwoods, x = 105.61 cm dbh). The habitat associations of this population indicated that the mild climate in the study area did not constrain their habitat selection and associations overall were consistent with other studies.
Recommended Citation
Chow, Nola, "Distribution and Habitat Associations of Northern Spotted Owls in Marin County, California" (2001). Cal Poly Humboldt theses and projects. 2640.
https://digitalcommons.humboldt.edu/etd/2640