Because spotted owls (Strix occidentalis) are territorial, the theory of habitat selection predicts that they should occupy sites that are relatively dispersed. We examined this prediction using data from a long-term study by measuring the spatial dispersion of occupied sites within years, and the spatial dispersion of sites relative to their occupancy among years. We also examined how experience, based on individual origin (local or immigrant recruit), and age of individual, influenced settlement distance relative to already occupied sites. We estimated that occupied sites were more dispersed than expected by chance, and sites with similar occupancy rates were dispersed rather than clumped. However, immigrants tended to settle closer to already occupied sites compared to individuals that switched sites within the study area. This suggested that immigrants might have been using conspecifics as cues to settle in potentially suitable habitat. Such a pattern of settlement may have long-term consequences on population dynamics if spotted owls select sites based on something other than intrinsic quality. Further, these results also suggest spotted owls may be slow to re-colonize areas once they have been extirpated.
Bibliographical noteFunding Information:
We thank Richard Skaggs, Alessandro Massolo, Alberto Meriggi, Michelle Crozier, David Grandmaison, Cynthia Hsu, and Guthrie Zimmerman for helpful suggestions on the analysis and preparation of this manuscript. This study was funded by the U.S. Forest Service (contract #FS53-91S8-00-EC14 to R.J. Gutiérrez), and the University of Minnesota.
- Conspecific attraction
- Spatial dispersion
- Spotted owl
- Strix occidentalis