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Full Description
The Northern Spotted Owl, a threatened species that occurs in coniferous forests in the western United States, has become a well-known environmental symbol. But how is the owl actually faring? This book contains the results of a long-term effort by a large group of leading researchers to document population trends of the Northern Spotted Owl. The study was conducted on 11 areas in the Pacific Northwest from 1985 to 2008, and its objectives were both to evaluate population trends and to assess relationships between reproductive rates and recruitment of owls and covariates such as weather, habitat, and the invasion of a closely related species, the Barred Owl. Among other findings, the study shows that fecundity was declining in five populations, stable in three, and increasing in three areas. Annual apparent survival rates of adults were declining in 10 out of 11 areas. This broad, synthetic work provides the most complete and up-to-date picture of the population status of this inconspicuous forest owl, which is at the center of the complex and often volatile debate regarding the management of forest lands in the western United States.
Contents
INTRODUCTION STUDY AREAS FIELD METHODS ANALYTICAL METHODS DEVELOPMENT OF COVARIATES Barred Owl covariate Habitat covariates Weather and climate covariates Land ownership, ecoregion, and latitude covariates Reproduction covariate FECUNDITY Individual study areas Meta-analysis of fecundity APPARENT SURVIVAL Individual study areas Meta-analysis of apparent survival ANNUAL RATE OF POPULATION CHANGE Individual study areas Estimates of realized population change Meta-analysis of annual rate of population change STATISTICAL CONVENTIONS WORKSHOP PROTOCOLS RESULTS FECUNDITY Individual study areas Meta-analysis of fecundity APPARENT SURVIVAL Individual study areas Meta-analysis of apparent survival on all areas Meta-analysis of apparent survival on the eight NWFP monitoring areas Potential cost of reproduction on survival Effects of Barred Owls on recapture and survival ANNUAL RATE OF POPULATION CHANGE Individual study areas Estimates of realized population change Meta-analysis of annual rate of population change DISCUSSION FECUNDITY APPARENT SURVIVAL ANNUAL RATE OF POPULATION CHANGE AND REALIZED RATES OF POPULATION CHANGE Individual study areas Meta-analysis of annual rate of population change STATUS OF OWL POPULATIONS IN THE EIGHT NWFP MONITORING AREAS ASSOCIATIONS BETWEEN DEMOGRAPHIC PARAMETERS AND COVARIATES Cost of reproduction on survival Weather and climate Barred Owls Habitat POTENTIAL BIASES IN ESTIMATES OF DEMOGRAPHIC PARAMETERS Fecundity Apparent survival Annual rate of population change Estimating goodness-of-fit and overdispersion SUMMARY, CONCLUSIONS, and RECOMMENDATIONS ACKNOWLEDGMENTS LITERATURE CITED APPENDICES TABLES FIGURES
