Comparing Avian Detection and Occupancy in Two Habitats in Todos Santos, BCS, Mexico
Category: Research Poster
Author(s): Hazel Shelton, Ashton Winter, Sabrina Fales
Presenter(s): Hazel Shelton
Mentors(s): Dana Winkelman
Desert ecosystems vary in vegetation structure, resource availability, and microclimate, which influence avian community composition and habitat use. Studies in the Chihuahuan and Sonoran Deserts have found differences in the breeding bird communities and habitat associations between scrubland and riparian habitats. Our study focuses on how bird occupancy and detection probability vary between surveys in arroyo and upland desert scrub habitats southeast of Todos Santos, a coastal town in Baja California Sur, Mexico. We used a modified point count protocol to survey randomly selected sites in arroyos and desert scrub and collected data about the vegetation structure at each point. We then created models in Program MARK to identify the variables that most significantly influenced detection probability and to quantify the occupancy of each habitat type. We found that the arroyos had higher occupancy than the desert scrub. Detection probability was greater in surveys done within two hours of dawn than those conducted within two hours of dusk. We found that vegetation structure did not meaningfully impact detection probability in either habitat. Arroyos support greater bird diversity, including species that use the arroyo specifically. Desert scrub supports species that we did not detect elsewhere, suggesting that some species rely on that habitat specifically. Thus, arroyo and desert scrub habitats should both be protected, despite the relatively low species richness in the desert scrub. Future studies would benefit from prioritizing morning surveys if the desired outcome is to maximize passerine detection.