4 ideas
Its body temperature had dropped far below normal and its breathing was nearly undetectable, and it returned to the same crevice in later winters. This was the first scientifically documented case of a bird hibernating, and it confirmed what the Hopi name for the bird, 'the sleeping one', already implied. Teale visits the site and uses the episode as a centerpiece of how life gets through winter.
A single season is not one condition but a gradient spread across a continent at the same moment. There is near-spring warmth on the southern and Pacific edges and deep snow in the north. By moving through geography during one season, an observer sees in weeks the range of winter's forms that a stationary observer would never witness together, so the road trip becomes a way of sampling the whole season at once.
Living things meet winter through three broad strategies. Sorting a creature by which strategy it uses explains its behavior and vulnerabilities through the cold months.
Winter looks barren only because its life is slowed, hidden, or small: buds holding next year's growth, animals in torpor, insects under bark and snow. Seeing it requires deliberate, close attention to details that summer abundance drowns out. The season rewards patient observation with evidence that the cycle of life never actually stops.