In summer the mountains are bustling with life. Songs of birds and insects fill the air and colorful forms flash from tree to tree. In contrast, the winter mountains are quiet and still. Some of the exuberant forms of summer die with the first frost. Many insects cannot tolerate cold and perish when the first ice crystals form on woodland soils, leaving only their eggs or developing larvae safely deposited beneath a blanket of fallen leaves.
Some mammals slip into burrows beneath the ground to sleep away the cold winter months.
Snakes seek shelter in crevasses, rock shelters, or used or unused mammal burrows. Box turtles dig their way beneath a sheltering layer of soil, while aquatic turtles seek the soft mud at the bottom of shallow pools. And many of our most colorful birds simply fly away. For thousands of years, bird migration was a mystery to humans. Observers of nature did notice that many birds as well as various other animals disappeared and then reappeared at certain times every year.