Population density and habitat use of the threatened Balsas screech owl in the Sierra de Huautla Biosphere Reserve, Mexico

Abstract

The Balsas screech owl Megascops seductus is a threatened species that is endemic to Mexico. We estimated the population density of the Balsas screech owl and evaluated habitat use during the dry season in the Sierra de Huautla Biosphere Reserve, Mexico. We estimated a total of 6.7 owls km -2 during the dry season (October 2001 to April 2002) by recording spontaneous calling and responses to playback of owl calls. October showed the highest density (12.2 owls km -2 ) and Feb- ruary the lowest (2.8 owls km -2 ); differences between months most likely were due to calling activity rather than density. Balsas screech owls used all 5 vegetation types identified in the Sierra de Huautla Biosphere Reserve; 4 were used in proportion with their availability, and Gliricidia-Caesalpina forest was used significantly less than its availability. There was significant variation in the number of owls recorded across different vegetation types. Conserved dry forest had the highest number of owl records, followed by thorn forest, disturbed forest, agricultural systems, and the fewest records in Gli- ricidia-Caesalpina forest. In order to design effective conservation plans for this threatened endemic owl, future research should prioritize population trends in various parts of its range and gather life history information.