MEXICAN SPOTTED OWL NEST- AND ROOST-SITE HABITAT IN NORTHERN ARIZONA

Abstract

The recovery plan for the Mexican spotted owl (Strix occidentalis lucida) recommended protection of owl nesting and roosting habitat. Descriptions of microhabitat (≤0.04 ha) characteristics associated with suitable nesting sites have been limited for the area of pine–oak forest occupied by this species in Arizona, USA. Therefore, we studied Mexican spotted owl habitat on a 585-km2 study area on the Coconino Plateau near Flagstaff, Arizona. Mexican spotted owls nested primarily in mature (≥45.7-cm diameter at breast height [dbh]) Gambel oak (Quercus gambelii; 40%) and ponderosa pine (Pinus ponderosa; 37%) trees. We examined a plausible set of a priori models using both standard logistic regression and matched pairs logistic regression under a model-selection framework. Our results suggested that spotted owl nest and roost sites were located on steeper slopes with greater percent canopy closure and greater mature and old-growth tree basal area than random sites. The presence of mature and old-growth hardwood trees was an important factor distinguishing spotted owl nest sites from all other plot types. We recommend management for mature and old-growth trees, and for large (≥45.7-cm dbh) oak trees in particular. In addition, due to the importance of oaks as a resource for nest and roost sites, we recommend a ban on fuelwood harvest of oaks. We present, for the first time, physical characteristics of Mexican spotted owl nest structures, which will aid resource managers in identifying potential nest sites in the field.