Meeting Abstract
Reproduction is an energetically expensive activity for parents and keeping endothermic offspring at their thermal optima represents a significant energy cost. Avian offspring develop optimally at ~39˚C. The tropics are generally thought to provide warm ambient conditions that require less effort to keep offspring warm. Yet, the synergistic effects of high rainfall and winds that characterize the mid-montane tropics may exacerbate heat loss and mean that the energetic costs of keeping altricial offspring at optimal temperatures are substantially higher than previously imagined for the tropics. However, the building of enclosed and thus sheltered nests may enable birds to buffer the effects of adverse weather conditions. Here we provide experimental and observational evidence that ambient temperatures in the tropics are ~20°C below the thermal optima of 39˚C and that rainfall and wind synergistically combine to increase the energetic costs of keeping offspring at thermal optima. Meanwhile, those costs varied between nest types, with species building enclosed nests saving significantly more energy than species building open nests. Our measurements and experiments demonstrated that rainfall, wind and their synergistic effect induces convective cooling that dramatically increases the costs of keeping endothermic offspring at their thermal optima in tropical regions. However, nest design can mitigate those costs and provide an important way of enabling animals to adapt to adverse environmental conditions in biodiversity-rich, but anthropogenically-threatened, tropical regions. (NSF: IOS: 1656120).
