Hummingbird foraging preferences during extreme heat events.

Climate change is projected to increase global mean annual temperatures as well as the frequency and intensity of extreme heat events. These changes are anticipated to alter the behavior of animals as they seek to thermoregulate in extreme heat. An important area of research is understanding how mutualistic interactions between animals and plants, such as pollination, will be affected by the cascading effects of extreme heat on animal foraging behavior. In this study, we used an experimental and observational approach to quantify the effects of extreme heat on hummingbird foraging preferences for nectar sources in shady versus sunny microsites. We also quantified pollen deposition using artificial stigmas at these sites to quantify potential cascading effects on plant reproduction. We hypothesized that hummingbirds would respond to extreme heat by preferentially foraging in shady microsites, and that this would reduce pollen deposition in sunny microsites on hot days. We found little support for this hypothesis, instead hummingbirds preferred to forage in sunny microsites regardless of ambient temperature. We also found weak evidence for higher pollen deposition in sunny microsites on hot days.