干旱区生态环境知识资源中心

Water affects distribution of many species, but climate change is set to change rainfall patterns and hence water availability. In South Africa, various global climate-change models suggest a drier future for the winter rainfall regions with implications for survival of plant and animal species of the fynbos region. Most birds offload heat by evaporative water loss, and this increases exponentially from 25 degrees C. Birds need to replenish their water loss to cope particularly at high temperatures, especially species that have little preformed water in the diet. We documented bird species drinking at five natural water sources at a semi-arid fynbos site through time-lapse cameras to explore which birds are drinking when. We modelled the total numbers of birds observed drinking as a function of diet, mass and relative abundance and found that species classified as granivores were predicted to drink most frequently, with the more common species most frequently recorded. A phylogenetically controlled trait-based logistic regression indicated abundance as the best predictor of observation at the water sources. Daily drinking rates at the species level for the ten most frequently observed species were generally best explained by daily temperature, with higher drinking rates on hotter days. However, daily drinking patterns were poorly explained by diurnal temperature trends at the hourly level, and we were unable to document sufficient predators to comment on the influence of predator avoidance or other heat mitigation strategies. Finally, we discuss the implications of our observations for the set of fynbos endemic passerines.