1.5-minute read
When it comes to achieving a serious level of avian chill, according to research from the University of New Mexico, South American hummingbirds are in a league of their own. These mini masters of hovering flight can significantly lower their overnight body temperature and rate of metabolism to ensure they live to fly another day. This short, inactive state, referred to as torpor in biology lingo, is similar to a very compressed period of hibernation. For hummingbirds that live in cold, high-elevation habitats, having the ability to enter a state of deep torpor is essential to their survival.
Researchers studying torpor as an adaptation to extreme environments in six species of tropical hummingbirds native to the Andes recently recorded the lowest body temperature to date amongst birds—3.26 °C in the black metaltail, aka Mettalura phoebe. By comparison, the body temperature of animals that hibernate for many days or weeks, like bears, groundhogs, and hedgehogs, drops to about 5 °C.
So why have these zippy, little nectar sippers developed such an exceptional chill skill? For an animal that weighs between 2 and 4 grams and has the highest mass-specific metabolic rate of any vertebrate, surviving in a cold, wet, low-oxygen environment is no small feat. To maintain its body mass, a hummingbird’s daily intake of nectar can exceed its total weight. According to the National Park Service, an average man would have to eat 285 pounds of meat daily to maintain his weight if he had the tiny bird’s metabolism. That’s one Whopper patty a minute for 19 hours! Plus, sustaining hovering flight of up to 4,000 wing beats per minute at 4,000 metres above sea level takes an incredible amount of energy.
To help maximize their fat reserves, Andean hummingbirds boost their caloric intake before bedtime and roost in thermally insulated caves, but torpor is their survival superpower. The more time hummingbirds spend torpid overnight, the lower their energy loss. Apparently, hummingbirds that deeply chill while they snooze don’t lose, and that energy conservation is one of the primary reasons why these mesmerizing creatures can persevere in harsh mountain environments. Isn’t evolutionary adaptation remarkable!
Speaking of hummingbirds, if you’d like to give your back-to-school brain a rest why not take a crack at the Audubon Hummingbird Wing Beat Challenge! Gather the kids or your favorite avian-loving adult(s) and see if you can flap your arms as fast as a hummingbird beats its wings. Start slow and try to match the American crow’s 20 wing beats per 10 seconds and then see how close you can get to the 500 wing beats of the broad-tailed hummingbird. Full disclosure, we only made it to 50 before we strained muscles that we didn’t know we had, but we bet you can top that. Happy flapping!
