Anthropogenic and Environmental Factors Affecting Avian Species Richness and Occurrence in an Ecological Oasis within a Desert Ecosystem

Abstract

Understanding the effects of anthropogenic and environmental factors on species richness and occurrence is important for conservation. Still, comparatively fewer efforts are conducted in areas of low species richness, such as deserts. We estimated avian species richness and occurrence in response to environmental factors and anthropogenic activity in Aldesa Valley, Saudi Arabia. Because of the presence of permanent water and associated vegetation in the valley, this region is suitable to support high biodiversity. During a two-year study, we divided the valley into 40, 250 m-segments and used time area-searches from May 10 to August 10 in 2014 and 2015 to estimate bird species richness and occurrence. We used generalized linear models to assess drivers of species richness. We analyzed the local distributions of the six most commonly detected bird species: House Sparrow Passer domesticus, Laughing Dove Spilopelia senegalensis, Tristram's Starling Onychognathus tristramii, White-spectacled Bulbul Pycnonotus xanthopygos, Palestine Sunbird Cinnyris osea, and Sinai Rosefinch Carpodacus synoicus using occupancy modeling. We recorded 24 avian species belonging to 18 families and seven orders. Observed species richness was positively correlated with search duration, segment area, and extent of herbaceous coverage. Ecological covariates influential in determining occupancy varied across commonly-observed species. Tristram's Starling selected for sand areas, unlike the House Sparrow who appeared to avoid sand and rocky areas. Palestine Sunbird occupancy was positively correlated with herbaceous cover types. Species detectability was overall positively correlated with search duration. House Sparrow's detectability was negatively correlated with tree canopy area. Signs of anthropogenic activities (such as number of vehicles, people, and domestic animals) affected detectability for species differently e.g. positively for House Sparrow and negatively for Palestine Sunbird.