(noun) A state of slowed body functions used to conserve energy and heat. Animals that enter a state of torpor lower their body temperature and slow their heart rate, respiration and metabolic rate dramatically, effectively conserving energy because fewer calories are needed to maintain life. Metabolic rate can actually decrease up to 95 percent. This type of short term hibernation can help animals and birds survive cold temperatures, and this state is most frequently used on winter nights. Some birds will also enter a torpid state if food supplies are scarce.
Torpor can be dangerous because a torpid bird’s reflexes and reaction abilities are also stunted, making them more vulnerable to predators. It can take several minutes to awaken from torpor, and a ready food source should be available for the bird to replenish its energy supply immediately. Many birds first come out of this sleep-like state through shivering, and they may sun themselves for several minutes while awakening.
Bird species that regularly use torpor include: