Lucy HicksHigh in the Andes, thousands of meters above sea level, speedy hummingbirds defy near-freezing temperatures. These tiny flyers endure the cold with a counterintuitive trick: They lower their body temperature—sometimes as much as 33°C—for hours at a time, new research suggests.“It’s a capacity that’s just incredible,” says Anusha Shankar, a physiological ecologist at the Cornell Lab of Ornithology, who was not involved with the study.Among vertebrates, hummingbirds have the highest metabolism for their size.
With a metabolic rate roughly 77 times that of an average human, they need to feed nearly continuously. But when it gets too cold or dark to forage, maintaining a normal body temperature is energetically draining.