Winter 2004

By Jack MacRae

Here's what's debuting on nature's stage in Chicago Wilderness

EARLY WINTER

Red-shouldered Stranger
Early last winter, a red-shouldered hawk began working the morning shift at the northwest corner of Glenview Road and the Edens Expressway. He (she?) arrived at the end of November and left abruptly, without giving his two weeks notice, in March. Many thousands of human commuters would pass him daily as he performed his duties as a rodent control specialist. Such a skilled, experienced worker is a valuable asset to any enterprise.

Male and female red-shoulders live apart in winter — they'll re-establish their pair bonds in the spring. They prefer to breed in wet woodlands and river valleys, with plenty of rodents.

Water Penny Lane
Water pennies are one of the wonderful macroinvertebrates (creatures lacking a backbone and visible to the naked eye) that live in the swift riffles of our clean streams. And, if you don't mind getting really cold fingers, you can find them in the winter. Water pennies are coppery brown and the size of an aspirin, but much flatter and flexible. They're found on submerged rocks, clinging securely to the slick layer of slime that also serves as their food. They travel slowly, grazing on the periphyton (a tasty blend of algae, bacteria, fungi, and protozoa) as they move.

Water pennies are the larval, aquatic stage of a small beetle. Over the organism's two-year life span, it will undergo a complete metamorphosis.

The larva will turn into a pupa (something like a butterfly's chrysalis) above the water line, with the emergent adult beetle staying close to the water. The adult is thought to be short-lived. It breeds but most likely does not feed.

MIDDLE WINTER

Mutilated Mice
At the risk of sounding like a Warren Zevon song, last winter I found nine headless mice on a gravel trail. Evidently something had eaten their brains. It looked like the work of a weasel, a ferocious predator with a fondness for organs. Perhaps the culprit was a least weasel, the world's smallest carnivore, and an uncommon creature in our region. Least weasels are white in the winter and brown in the summer. The trail of decapitation passed through brushy habitat adjacent to a fen — an area well-suited for these secretive hunters, that need to eat half their body weight (one or two mice would do it) each day.

Way-Cool Snakes
In the winter world of reptiles, garter snakes are known as light sleepers. Through the years, there have been numerous local reports of active garter snakes in mid-winter. The details are similar: the snakes usually are spotted taking in the warm, early afternoon sun, close to the rocks or bricks in which they have been hibernating. Tolerance of cold is a trait of the garter snakes — they are the most northerly snake in North America.

To Live and Die in a Gall
Next time you're taking a cold stroll through a grassland, check out the big, round galls on the goldenrod stems. They're notable examples of co-evolution and the complexity of nature. Galls, formed last summer, are the plant's response to a larval insect living and growing inside the stem.

All is not safe inside a gall. During the winter, both black-capped chickadees and downy woodpeckers (see page 31) adeptly extract the squishy, high-calorie maggot morsels. Holes made by a chickadee's stout, pointed beak are larger and more ragged than the neat, round holes made by the woodpecker. If a goldenrod-gall larva survives until spring, it will morph into a picture-wing fly.

LATE WINTER

Trespassers Will Be Violated
By the ides of March, male coyotes have staked out their territories, establishing a fragile yellow border in their special way. Females will be house-hunting. During this time of year, coyotes have little tolerance for foxes, which they see as competition. Dogs are not appreciated either. Noted bat enthusiast Ozzy Osbourne lost his little black Chihuahua to a coyote last year. True story.

If you want to sound impressive at a holiday party, use the term "RLUs" in casual conversation. It's short-handed jargon for "raised leg urinations" and is used by coyote and wolf researchers in population and behavior studies.

Early Mourning
Mourning cloaks are one of a few local butterflies that hibernate as an adult. During winter, they practice a natural form of cryogenics, relying on a self-made antifreeze, sorbitol, to stay alive. They fly as soon as the air begins to warm and are often spotted in March, flying through our oak and maple woods and more open areas. On occasion, I've found them flapping in the bottom of sap-collecting buckets.

Mourning cloaks hold the North American record for longest life span (butterfly category). Some will live for 11 months.