The fur of snowshoe hairs turns white to help them adapt to winter conditions. ISLANDER FILE PHOTO

Winter forces adaptation



A new year has begun, and in January, we no doubt will experience the cold and harsh weather of a Maine winter. Humans cope by creating wood piles, putting on snow tires and layering our clothes. Native mammals have thicker fur and maybe a change of color to match the snow, as do snowshoe hares and ermine. Whenever possible, after snow has fallen, small mammals travel more safely in their tunnels beneath the snow. In these tunnels, they can travel across wide-open areas and in the woods unseen by their predators. It also consequently makes hunting a little more difficult for foxes, owls, etc.

A few inches of snow does not create trouble for animals such as foxes, but if the snow deepens to six inches or more, these mammals must bound through it to move about, thereby expending more energy at a time when it is harder to find food. Deer become vulnerable then to dog attacks. When deep snow slows their escape, dogs hunting them can run on the surface, while the deer break through the crust. When the weather gets cold, the feet of partridge are doubled in size by small comb-like projections that grow on either side of the bird’s toes. This makes the birds a pair of built-in “snow shoes.” Watch for their tracks after a snowfall. Any mammal not able to adapt to the winter scene is not part of it.

Another northern shrike was seen this week but this time in the Bar Harbor area. The bird is usually a loner, and you spot it sitting in the top of a tree. We can expect to see them here on the island from October through April. One may surprise you with a visit to your feeder. It will be unfortunate for some individual bird there getting caught, but the shrike is such an interesting bird itself you really can’t begrudge it its lunch. The northern shrike is robin-sized with a heavily hooked beak, black mask and large white wing patches. It usually perches out in the open, on a wire, telephone pole or small tree or shrub.

The shrike’s nickname is “butcher bird,”’ which comes from its habit of hanging its catch, be it insect, mouse or bird, on a thorn, as if it were a butcher skewering a hunk of beef. A shrike’s feet are not as strong as those of a hawk, so the shrike impales its food, then tears off the meat it eats with its stout bill. Shrikes do take a few birds, but their main diet includes mice and insects when available. Shrikes move about singly. You would never see a flock of shrikes. Nature has everything planned well.

A letter to me this week asked about oak branches she was finding broken off – maybe bitten? – and on the ground under a healthy oak tree. Her question sent me to my references for the answer. I suspected that a mammal of some sort, possibly a gray squirrel was involved. The answer was a little more complicated.

There is a small creature called the oak twig pruner that may have been at work. The larva of this creature cut through the twig, causing it to fall off eventually. The twig pruner cuts through the twig from the inside, but the leaves and bark remain intact. For a short time, the injured branch remains on the tree, but it eventually succumbs to the wind, breaks off and falls to the ground. A small oval-shaped hole in the end of the branch is a tell-tale sign of the twig pruner. Check your branches! According to the Maine Department of Agriculture, the oak twig pruner is not a significant threat to tree health and spraying is not recommended. If you want more information about this, it is available online.

Squirrels, of course, come to mind with such evidence, and gray squirrels are active all winter. Here again, you should carefully examine the end of the twigs. If the twigs have a slanted cut end or a sheared-looking end, squirrels are likely culprits. They sometimes bite the stems and use the leafy twigs to make their winter nests. This activity is no problem for the tree. Squirrels may chew on branches, keeping their teeth tidy and in good working condition. Some squirrels will go after the bark that comes from the highest branches of trees. Eastern gray squirrels are especially known for this. They pull off the branches to get needed sodium, since the sap beneath the bark is packed with sodium.

A friend visiting Connecticut over the holidays saw a flock of bluebirds on Christmas Day. What a nice present! We don’t see bluebirds here on this island very often anymore and certainly not in winter. Bluebirds are on the rare bird list these days on this island. Their numbers have been decimated by the introduced English sparrow brought here in the late 1800s from England. The English sparrow, also called the house sparrow, is very aggressive and takes over any bluebird nest, even pecking the bluebird to death as it sits on its nest and eggs. Bluebirds are not at all aggressive. Each year here on Mount Desert Island, a few bluebirds are seen in a couple of places, but they are a rare sight. Introducing birds, and I might add many plants, from one country into another country with no thought to the consequences is never a good idea. Through the years, it has always led to many problems in the environment.

If you walk along the shore this month, keep watch for purple sandpipers on the rocks and right at the edge of breaking waves. They are large, portly looking, dark sandpipers traveling in a small flock together. They feed right at the edge of the sea, especially near rocky jetties. Let me know if you see any, please.

Ruth Grierson

Ruth Grierson

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Send any questions or observations to [email protected] or call 244-3742.
Ruth Grierson

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