Population ecology of the spotted owl in the central Sierra Nevada, California
Graduation Date
1992
Document Type
Thesis
Program
Other
Program
Thesis (M.S.)--Humboldt State University, Wildlife Management, 1992
Committee Chair Name
R.J. Gutierrez
Committee Chair Affiliation
HSU Faculty or Staff
Keywords
Owls, Bird populations, Spotted owl, Sierra Nevada, Humboldt State University -- Theses -- Wildlife Management
Abstract
I studied the demography of California spotted owls(Strix occidentalis occidentalis) in the central Sierra Nevada, California between 1986 and 1989. Fifty-five spotted owls were banded during the study. Estimates of fecundity, nest success, and productivity were 0.34, 42.0%, and 1.70, respectively. Of thirty-nine territories monitored, on average 55% and 21% were occupied by pairs or single owls, respectively, while 24% were unoccupied. Population size was estimated empirically, from Jolly-Seber models A and D, and from Leslie regression analysis. The population estimates were 36, 33, 32, and 40 birds, respectively. All estimates were statistically the same. Goodness of fit tests indicated that the data from this study satisfied the assumptions of the Jolly-Seber models. Crude density was 0.09 owls/km2 and was significantly less than that reported for the northern spotted owl. Standard Lotka-Leslie models were used to assess the sensitivity of A to variation in the vital rates and to project population trends. Parameters estimated were adult survival rate (S) = 0.76, juvenile survival rate (S0) = 0.16, and fecundity = 0.34. The empirical estimate for adult survival was not significantly different from the Jolly-Seber model A estimate. The population's finite rate of growth, λ, was most sensitive to adult survival rate and age of senescence. Fecundity, subadult, and juvenile survival rate did not dramatically influence estimates of A. The value of A for this population was 0.811, which was significantly less than 1.0. At this rate of decline the population's half life is 4 years.
Recommended Citation
Lutz, Daryl W., "Population ecology of the spotted owl in the central Sierra Nevada, California" (1992). Cal Poly Humboldt theses and projects. 1400.
https://digitalcommons.humboldt.edu/etd/1400
https://scholarworks.calstate.edu/concern/theses/pg15bh27p