Better Understanding the Barred Owl

This thesis research presents an analysis of barred owl nest site selection in an understudied region of their expanded range. The barred owl has dramatically expanded its range westwards over the last 150 years, prompting multiple conflicting reinterpretations of their species account. Hypotheses of range expansion are reviewed to provide context for this study’s research. This study gathers empirical data on nest site selection in the mixed conifer forests of Montana’s Seeley-Swan and Mission Valleys. Eight barred owl nests were located following extensive territory surveys. Field measurements of tree height and diameter using USFS Forest Inventory and Analysis (FIA) plot design were conducted around each nest and compared statistically to unoccupied FIA plots located in the study area. Additional, coarser scales of analysis were also assessed via raster GIS analysis of USFS Tree Canopy Cover (TCC) data and NASA Global Ecosystem Dynamics Investigation (GEDI) tree height LiDAR data. Findings from all of these comparisons indicate barred owls are selecting nest trees in stands (possibly around an acre) with above-average tree size and canopy cover, as well selecting nests within a larger forest matrix (100 m+) with above-average canopy cover. These findings align with the traditional understanding that they prefer contiguous, mature forests. However, nest stand values did not greatly exceed random stand values (e.g. mean nest stand height = 18.8m, mean FIA control plot height = 17.2m), which aligns with the growing consensus that the species is more adaptable than traditionally assumed.