Urban birds in the Sonoran Desert: estimating population density from point counts

摘要

We conducted bird surveys in Hermosillo, Sonora using distance sampling to characterize detection functions at point-transects fornative and non-native urban birds in a desert environment. From March to August 2013 we sampled 240 plots in the city and itssurroundings; each plot was visited three times. Our purpose was to provide information for a rapid assessment of bird density in thisregion by using point counts. We identifed 72 species, including six non-native species. Sixteen species had suffcient detections toaccurately estimate the parameters of the detection functions. To illustrate the estimation of density from bird count data using ourinferred detection functions, we estimated the density of the Eurasian Collared-Dove (Streptopelia decaocto) under two differentlevels of urbanization: highly urbanized (90-100% of urban impact) and moderately urbanized zones (39-50% of urban impact).Density of S. decaocto in the highly-urbanized and moderately-urbanized zones was 3.97±0.52 and 2.92±0.52 individuals/ha,respectively. By using our detection functions, avian ecologists can effciently relocate time and effort that is regularly used for theestimation of detection distances, to increase the number of sites surveyed and to collect other relevant ecological information.