Hummingbirds Torpor Journaling Question Discussion (Back to Lesson) Why is a 3-gram chunk of clay so tiny compared to a hummingbird that weighs the exact same? Clay is dense, with little air inside. Hummingbird muscles are almost as dense as clay, but their bodies also contain large air sacs and hollow bones, and are covered with a relatively thick layer of feathers, which are feather light. So a hummingbird body has far less density than a piece of clay. That may be why hummingbirds have an easy time flying but when people are slow and sluggish and even have trouble walking, we say they have "feet of clay." Why do you think no large birds undergo nighttime torpor? Laura Erickson notes that in the same way that a tiny piece of clay cools off quicker than a bigger piece of clay when put in the refrigerator, it takes longer for a big piece of clay to warm up. It takes a hummer about an hour to get back to normal when its body temperature has dropped to 20 degrees C in torpor. It would take a Blue Jay-sized bird over 12 hours to get back to normal. By then it would be nighttime all over again! Facebook Pinterest Twitter © 1997 – 2019 Journey North. All rights reserved.