Abstract

We report the first quantitative information on the relative abundance of rufous-legged owls (Strix rufipes King) in six secondary and five old-growth rainforest remnants of southern Chile. Over 62 nights spanning four years, we surveyed 37 linear km of secondary- and 49 km of old-growth forests, detecting the presence of 0.127 and 0.220 owl pairs/km, respectively. Canopy cover accounted for 68% of the variance in owl abundance, based on a stepwise regression. Mean diameter at breast height (d.b.h.) and number of snags/hectare each accounted for only 2% of the unexplained variance; stand age accounted for very little of the residual variance. When removing canopy cover from the stepwise regression, mean d.b.h. accounted for 34% of the variance in owl abundance; adding snags/ha improved it by less than 1%, and stand age explained less than 8% of the residual variance. Similar to the spotted owl (Strix occidentalis Xantus), the rufous-legged owl is closely associated with old-growth stands. In addition, the core of both owls' diets is mostly arboreal and scansorial small mammals. As southern Chilean old-growth forests disappear due to logging, the odds for the long-term survival of the rufous-legged owl are becoming lower.