ACT's Nature Corner: Sounds of Winter
By Maine Master Naturalist, Joan Hull
Winter is a wonderful time for a walk in the woods, often you’ll have the trail to yourself. Ever notice how clear and crisp sounds seem in winter? Why do you think that is? Surely part of it is so many competing sounds are missing, no insects buzzing, no whispering of leaves and grasses, no fall leaves rustling or crunching underfoot. The sounds we do hear seem so much louder. There are also laws of physics that explain why sound in winter seems louder.
Sound is generally absorbed by soft things and reflected by hard things. In the warm months, the soft earth absorbs sounds, in the cold hard New England winter the frozen earth, ice and crusty snow will bounce sound back to our ears. After a fresh snowfall, sound will appear somewhat quieter as the soft snow absorbs the sound until a hard crust is formed. Air temperature can also affect sound. Sound travels faster in warm air than cold air, but we can often hear sounds from further away in cold air. When the air is cold during a winter day the atmosphere above is usually warmer. When sound waves move from the cold earth to a warm layer of air above they are bounced back to our ears from greater distances.
Enough of the physics. Winter walks for me are a time to focus on listening. So many sounds, some are comforting old friends like the chick-a-dee-dee-dee of the black capped chickadee, our state bird of Maine.
Then there is the harsh drumming of the pileated woodpecker, which can be heard a half mile away along with its crazy cackle of a call. Maine’s largest woodpecker at up to 19 inches long with a wingspan of almost 30 inches is beautiful to see with their large triangular flaming red crests. The male sports an additional red stripe on his cheek. If you don’t hear one on your walk, be on the lookout for signs of where they might have been. If you see what looks like fresh wood chips at the base of a dead tree look up. If you see a series of oval or rectangular holes from 31/2 to 8 inches long a pileated woodpecker has been looking to find its favorite food, carpenter ants in the dead wood.
The holes will become homes for other birds and even ducks when the pileated abandons the tree. Below are links to the distinctive drum and cackle call of the pileated woodpecker.
The trees in the woods have their own special winter sounds from the soft “whoomph” of a soft pile of newly fallen snow falling from branches above to the mysterious booming that can sound like a gunshot. Take care when you hear the “whoomphing.” Many times, I didn’t take heed and had snow careen down the back of my neck. Not the most comfortable way to continue your walk.
Once you are back from your walk in your warm home with a cup of hot chocolate or something stronger I would recommend clicking the link below and read the short story “To Build a Fire” by Jack London. You will get a much different perspective on the power of a “whoomph”.
One of the most loud and startling sounds I’ve ever heard on my winter wood walks is the booming of trees. At first it sounds like a branch has broken and will come crashing down but I see no broken limbs. What I have found is a tree that has a split in its bark like the picture below.
It usually happens later on a sunny day when it is beginning to get cold again as evening is approaching. The cracks are more commonly found on the south or west side of the tree and are more common on smooth or dark bark trees. A common thought was that it was the trees’ sap that was “exploding” due to the sudden change in temperature. We have now learned that in winter, trees that lose their leaves like maples and oaks store most of their sap below ground in their root system during the winter and conifers have sap that does not freeze. There still is water in the trees’ cells however and the area surrounding these cells. On a warm sunny winter day, the sun warms the bark of the tree, particularly on the southern side where it is sunniest, and it expands in the heat. When it suddenly begins to get cold the bark begins to contract and when the temperature difference is too great or too fast the bark splits creating a loud crack.
Dark bark trees absorb more heat and so are more likely to crack particularly when they are younger, and their bark is smooth. Older dark bark trees have deep furrows in their bark that tends to dissipate the heat and give them some protection. Lighter bark trees like birches tend to reflect the sun’s heat that protect them, to a degree from great changes in temperature, however their bark is usually thinner and more susceptible to dramatic changes in temperature.
Next time you are on a winter walk see if you can find a tree with frost cracks. Look closely and try to figure out what happened. What side of the tree is cracked? What does the bark look like, dark or light, smooth or furrowed? Is the crack new or did it happen when the tree was younger? Have fun as you try to play tree detective.
The night in winter has its own particular sounds. My favorite is the call of the barred owl. This large owl (17- 20 inches long) does not migrate and so is around the entire year, but it's calls are most prominent towards the end of February and into March, their primary mating season. As their name suggests this owl has brown and white colored bars on their chests and wings. See the picture below.
These owls without hear tufts have very dark eyes and a yellow beak. They nest in hardwood cavities 20-40 feet high usually in mixed forests by water where they are most likely to find their favorite food on their night hunting forays. They are however much easier to hear than see with their distinctive “who cooks for you” call.
Walking outside in the winter is a special treat in Maine. Bundle up in the appropriate layers and enjoy the amazing sounds and sights that Maine has to offer in the winter. Take a deep breath and as your heart rate begins to slow so will the passing of time. What a treat.
What other sounds do you hear on your winter walks? Any mysteries? Share them or any comments at firstname.lastname@example.org. We’d love to hear your thoughts and experiences.