Opportunistic use of camera traps to assess the diversity of ground-dwelling birds in relation to environmental and anthropogenic variables in Tehuacán-Cuicatlán, Oaxaca, Mexico

Abstract

Semi-arid vegetation is predominant in Mexico, and the Tehuacán-Cuicatlán Biosphere Reserve is considered one of the most biodiverse semiarid protected areas in the country. The objectives of our study were to evaluate the diversity of ground-dwelling birds through the opportunistic use of camera traps set for monitoring mammal species, and to determine the relationship between bird diversity and 4 environmental variables (distance to rivers, tree cover, shrub cover, and environmental heterogeneity) and 5 anthropogenic variables (distance to roads, human settlements, and agricultural zones, and numbers of cows, donkeys, goats, and people) within the La Cañada region, located inside this reserve. We used bird records from 93 camera-trapping stations taken over the period 2011–2016. In order to evaluate the relationship of bird diversity with environmental variables, a subgroup of 36 camera traps was selected and analyzed using generalized linear models. We recorded a total of 30 bird species in >1,368 photographic records collected over 33,000 camera-trap-days. These birds belonged to 14 orders, 22 families, and represented 23% of the total number of species known to occur in La Cañada. A Clench species accumulation model estimated 38.5 ground-dwelling birds. Record frequency varied significantly among vegetation types and was greater in the crassicaule scrub and tropical deciduous forest (79% of the records). The diversity indices were higher closer to the rivers, and in areas with greater tree coverage and low human activity. High environmental heterogeneity positively influenced the higher diversity of ground-dwelling birds compared to that of sites at greater distance from water bodies or with little vegetation cover. Noninvasive techniques, such as camera-trapping, could be a complementary method for evaluating ground-dwelling bird activity, occupancy, and habitat use. We also recommend that similar opportunistic data of considerable biological and ecological value be published rather than simply archived.