Thermally-driven thresholds in terrestrial avifauna waterhole visitation indicate vulnerability to a warming climate

Warming global climates represent major threats to avian populations, particularly those reliant on surface water within arid biomes. We investigated terrestrial avian use of groundwater-dominated arid zone waterholes in central Australia to identify species vulnerable to climate change. Camera traps set in Watarrka National Park recorded avian species over 14 months at three waterholes during 2014 and 2015. Recorded species were assigned to functional groups, which included nectarivores, granivores, carnivores and omnivores. Generalised Additive Mixed Models (GAMMs) were used to model daily trapping rates (DTRs) for each functional group at waterholes in relation to daily maximum temperature and days since last rainfall. Granivores exhibited high DTRs across the entire daily maximum temperature range (15 °C–43 °C). Increasing threshold responses beyond specific daily maximum temperatures were exhibited by nectarivores (35 °C), carnivores (30 °C) and omnivores (30 °C). The DTRs for all functional groups increased with days since last rainfall. These data indicate species within all functional groups are vulnerable to a warming climate, even those that are considered to be surface water independent, as increasing waterhole visitations in torrid conditions reduces foraging time and could lead to reduced fitness in particular individuals.