To me, one of the first signs that Spring is beginning to make headway is seeing the leaves - only recently just tumbling over the cold hard snow - now taking on enough warmth to melt into the slowly softening blanket.
Northern Pin Oak trees usually keep most of their leaves throughout winter, and I enjoy hearing the breeze rustle through them - it adds a soft-sigh hint of life to winter's cold, short days. A stiff wind will loosen some of the leaves; throughout the winter you'll see occasional voyeurs skating over the snow, sometimes getting caught and building mini-snow drifts on their lee. They make for quite photogenic macro subjects, in an often otherwise (macro-photographically speaking) barren winter landscape.
It's a little rarer for me to catch the leaves acting as heat sinks like this one; together we're eagerly ushering Winter to Spring.