Long-Term Study of Owl Occupancy in Protected Areas of El Salvador

Abstract

ABSTRACT Understanding patterns in the occupancy of Neotropical owls can help inform land managers and conservation efforts; however, Neotropical owls are understudied compared to their temperate kin. We conducted the first long-term (10-yr) study of owls in El Salvador to assess occurrence patterns and species richness using occupancy modeling. Our study occurred in El Imposible National Park, Montecristo National Park, and Nancuchiname Forest, and we chose two survey routes per protected area to represent the landscape diversity of the country. Surveys involved passive listening and broadcasting calls of several species at selected points along each route, and we sought to repeat each survey route twice per year. We completed 86 surveys between March and May each year from 2003 through 2013, except in 2006 when no surveys occurred. We detected nine species of owls, including the Stygian Owl (Asio stygius), which was previously undocumented in El Salvador, and we documented 1211 owl records overall. We developed Bayesian, hierarchical, single-species occupancy models for the Mottled Owl (Ciccaba virgata), Ferruginous Pygmy-Owl (Glaucidium brasilianum), and Spectacled Owl (Pulsatrix perspicillata), and a multi-species richness model for all El Salvador owls. We found that the effects of broadcasting calls were species-specific (i.e., broadcasting some species' calls increased detection probabilities while others decreased detection). Nancuchiname Forest was the most species-rich, while the cloud forest of Montecristo National Park had several species that we did not observe elsewhere. In general, we found relatively stable occupancy patterns across the study period, and we recommend some specific areas of further study to inform management decisions.