News From The Mews

Normally it takes me a few moments to find our gray tree frog. His dark, mottled color camouflages impressively with the bark and branches in his habitat. But this morning, I watched him scramble up a piece of bark. He clung awkwardly between the bark and a plant, his legs stretched out so I could spy bright yellow on his foot. He soon found his footing and settled into a more comfortable position. His legs folded tight against his body, hiding the yellow patch, and he practically disappeared from view.

When Aldo the American Kestrel sits comfortably inside on cold winter days, part of me worries about Carson the Red-tailed Hawk still perched outside. But then I hear my mentor's voice in my head saying reassuringly, "she's fine - they're built to be here year-round." One adaptation that allows Carson to tolerate cold weather is one that she shares with all birds: cold feet. Birds can let their foot temperature drop to near-freezing to conserve their core body temperature. This is achieved through an efficient system called countercurrent heat exchange. Arteries carrying warm, oxygen-rich blood travel down the leg closely intertwine with veins. The proximity of the descending arteries and ascending veins allows heat to transfer across the blood vessels. Cold blood from the toes is passively warmed by the arteries as it heads back up to the body. How efficient! This system maintains the toes above freezing with a continued blood supply to avoid frostbite. Birds als...

Aldo comes inside when the outdoor temperatures dip below 10°F, so he has been in the office a lot recently. When people ask why, they often nod and answer their own question: "oh, because he's so small!" But size can't be the only way to explain this bird's winter hardiness.  Both my daughter and my cat delighted in watching chickadees at our bird feeder last weekend. Weighing in at just a half-ounce, chickadees are 1/7th the size of Aldo the American Kestrel. Yet they survived even through our recent -30°F nights.  My whole family was enthralled with watching the bird feeder at breakfast! Chickadees have fascinating strategies to cope with Wisconsin's winters. They ensure a food supply by hiding seeds in the fall, and enlarging the memory portion of their brain (hippocampus) by 30% to remember where those seed caches are located. Small owls, about the same size as kestrels, also overwinter here. They can locate prey under a blanket of snow with their amazing...