3.5 Wednesday, Jan. 4 Heat waves - challenges for desert bird communities WOLF, BO*; MCKECHNIE, AE; Univ. of New Mexico; University of Pretoria, SA email@example.com
For the avifaunas of hot subtropical deserts, among the most important, but understudied, direct effects of climate change may involve catastrophic mortality events associated with extreme heat waves and droughts. A number of large-scale die-offs during extremely hot weather have been documented in the past, and general circulation models predict increases in the intensity, frequency and duration of heat waves. Here, we identify the physiological mechanisms underlying avian mortality associated with heat stress and the lack of water, and develop a model that predicts rates of evaporative water loss and survival times during very hot weather as functions of body mass and dehydration tolerance. Applying our model to current and projected maximum air temperatures for two localities in hot subtropical deserts, we find that the increase in maximum air temperatures predicted for the 2080s will increase rates of evaporative water loss by more than 50-80% in very small birds, reducing survival times by 30-40%. For birds weighing < 100g (more than 80% of species in most desert bird communities), rates of evaporative water loss will increase by 30-50% and survival times will be reduced by at least 25%. The existing literature suggests that many species will simply be unable to up-regulate EWL to maintain body temperatures below critical lethal limits given the predicted increases in heat stress. Current and historical accounts already document catastrophic mortality caused by hyperthermia or through dehydration. Increasing global temperatures, combined with more intense and frequent heat waves, will result in more frequent die-offs among desert birds, potentially depopulating regional communities.