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INDIRECT EVIDENCE

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Beneath the big Shagbark Hickory outside our office window were a few empty shells with gnaw marks--indication that squirrels like hickory nuts as well as walnuts. But the ground was also littered with small branches from the hickory tree, some with dead and withered leaves still attached. The base of each twig bore a distinctive pointed tip surrounded by a smooth area that looked as if someone had started to whittle the twig from the tree and then simply broken it off. Amazingly, this initial precision cut was made by the powerful mandibles of a female Twig Girdler Beetle, Oncideres cingulata, that first had used her ovipositor to insert an egg into the horizontal hole just below the end of the twig. Then she bit through the wood so the twig would fall earthward and provide a winter feeding chamber for her larval offspring. Judging from all the horizontal notches on the twig in the photo, she must have had a hard time deciding exactly where to make her final cut.

And speaking of horizontal, that's the configuration of a series of round, quarter-inch holes (above) on the smooth gray bark of a young Sugar Maple tree growing not far from the hickory. Even though the maker of the holes wasn't around, there was absolutely no doubt what made them: Yellow-bellied Sapsucker. Several of these northern woodpeckers show up each autumn at Hilton Pond Center, where they visit a variety of hardwood trees, drilling their signature lines through bark and into the cambium layer. As sap oozes slowly from the holes, the sapsucker returns and laps up the dilute sugar solution with a tongue that has feathery edges rather than the barbs found on most woodpeckers. Insects are also attracted to the sap and become a source of fats and protein for the sapsucker. Interestingly, these "sapsucker wells" may play a crucial role in survival for spring migrant hummingbirds that arrive before wildflowers bloom. Hummers lap the sap like sapsuckers AND consume tiny gnats and midges that are too small for the woodpecker to be bothered with.

Moving down the trail, we crossed the bridge on the east end of Hilton Pond, where we noticed the water surface had a thin, oily sheen. Typically, the presence of an oil slick on a body of water is cause for alarm, but what we observed was a natural occurrence that betrayed the presence of yet another organism we couldn't see. In this case, we actually would have needed a microscope to view the oil slick's maker: the countless numbers of iron-fixing bacteria that thrive in Piedmont ponds and slow-moving streams. Folks familiar with the Carolina Piedmont know of its clay deposits stained red by iron compounds. As water flows over this clay and surrounding rocks, minute amounts of iron or its compounds dissolve and, in turn, are used in metabolic processes by iron-fixing bacteria--especially in relatively anaerobic situations. The sheen on the water is essentially a thin layer of insoluble ferric iron rust that breaks up easily when stirred--unlike petroleum slicks that tend to stay together. Thus, the oily-looking surface posed no danger to wildlife and simply indicated a relative lack of oxygen in the iron-rich, detritus-laden shallow water under the bridge.

After crossing over Hilton Pond we wandered into an open area that we maintain as a Goldenrod meadow--all the better to attract butterflies and other pollinators. By November, these insects have disappeared, some having passed their genes to new generations overwintering as egg, larva, or pupa. During early summer we heard the call of a Blue Grosbeak in this open spot but couldn't tell if he had a mate nearby. Now, however, a nest only three feet above the ground stood out starkly against the winter terrain--no longer camouflaged by leaves that died and fell this autumn from a scrawny one-inch-diameter Sweetgum tree. Woven onto a small branch and a tangle of Japanese Honeysuckle vines, the grassy nest incorporated a white paper bag that some fast food junkie had thrown from a passing car. We're not sure how we overlooked this litter-laden nest when we photographed nearby butterflies a couple of months ago, but if we couldn't spot the nest then perhaps local predators missed it, too.

As we neared the end of our trail-walking, a small pine about four feet tall attracted our attention, not because of its normal attributes but because something seemed to have stripped away much of the bark on its lower trunk. Ten years ago we would have had a hard time determining what caused this scar, but considering the time of year and recent sightings we knew that a buck White-tailed Deer had been scraping velvet from his emerging antlers. Our local deer population has increased significantly in the past decade--from zero to at least a half-dozen animals that move through the property. Scarcely a week goes by that we don't spot at least one, including new fawns and the famous "ghost deer"--a white (piebald) one that showed up on Christmas Day 2002. We suspect we'll find a lot more bark scrapings as the deer herds continue to grow.

On one day in the woods this week the only organisms we saw were plants, but there was no doubt other living things had been around: A twig girdler's nursery, the larder of a sapsucker, that bacterial sheen, on old grosbeak's nest, and the deer scrape from a buck that right this moment may be defending his rights as the rutting season unfolds. At Hilton Pond and elsewhere, such clues are all around us, and like detectives it behooves us to look at indirect evidence to know what's been going on in the world of nature.