Adaptation

July, like January, is the most extreme month of its season, and during both months I must adapt to challenging weather if I want to walk our trails and observe wildlife.

Black birches in the forest of Plummer’s Hollow

Black birches in the forest of Plummer’s Hollow (Photo by Dave Bonta on Flickr)

In January, when the wind is howling and it’s ten degrees Fahrenheit, I wait until mid-morning to venture outside swathed in several layers of clothes.

In July I try to be abroad by 8:30 a.m. dressed in as little as possible. That used to mean shorts and a tank top, but since ticks arrived on our mountain, I pull on long, beige-colored, Permethrin-soaked pants, which I tuck into light-colored socks, and a long-sleeved shirt over a tank top. Then, I put a wide-brimmed hat over my short hair and I’m off.

But last July the heat and humidity on many days was more debilitating than usual. Even 8:30 was too late on many July days for someone as heat-averse as I am.

The morning sun through the fog over the First Field

The morning sun through the fog over the First Field (Photo by Dave Bonta on Flickr)

We’ve been told that humans, plants, and wildlife must adjust to our changing climate. In that spirit my husband Bruce suggested I get up at 5:00 a.m., grab a cup of coffee, and go, instead of rising an hour later, preparing and eating breakfast, and following my normal hour of back and neck exercises before venturing outside.

That’s how I became a connoisseur of sunrises. Most dawns I rushed the quarter mile up to the spruce grove and Alan’s Bench at the top of Sapsucker Ridge. One morning the sky was golden and lit up the trees along the trail. On another, a rosy-fingered dawn predicted a clear, hot day ahead.

Near the end of July I watched the sky turn from gold to rose and finally pink before I reached Alan’s Bench. A sudden light flashed on the horizon as the sun appeared over Nittany Mountain, heralded by the drumbeat of a pileated woodpecker and the “witchedy, witchedy” of a common yellowthroat. As soon as it crested the mountain, I looked away from that burning eye that makes life on earth possible.

An ovenbird in Chester County, PA

An ovenbird in Chester County, PA (Photo by Kelly Colgan Azar in Flickr, Creative Commons license)

Instead, I sought the sanctuary of the forest as it filtered the fierce light through its green film of leaves.

Although birdsong dwindles in July, I listened to the dawn singing and calling of ovenbirds, red-eyed vireos, scarlet tanagers, eastern towhees, Acadian flycatchers, eastern wood-pewees, hooded and black-throated green warblers in the forest and common yellowthroats, song and field sparrows, indigo buntings, northern cardinals, Carolina wrens, cedar waxwings, and gray catbirds in the fields and yard.

One charmed morning I was serenaded by a chorus of wood thrushes as I walked down our road. The thrush music echoed in the outdoor cathedral of hundred-year-old trees looming overhead. I gave a silent prayer of thanks for their songs and hoped I would live to hear them another year. (I will embed a brief YouTube video of a singing wood thrush.)

On that same dawn walk I startled two does and two fawns that were standing in our stream. The fawns disappeared up the road bank while the does remained watching me for a few seconds before following their offspring.

A black rat snake

A black rat snake (Photo by Tom Walsh in Wikimedia, Creative Commons license)

I also found a black rat snake sprawled across the road. At first I thought it was dead, but as I stood above it and suggested it get off the road, it twitched its tail and curled up, looking as fierce as it could manage. I stepped carefully around it and continued on my way. Later, after the sun’s red disk shone through the trees and I retraced my steps, the snake had vanished.

Not all days were steamy. Early in the month, I devoted several cooler mornings to taking our 11-year-old granddaughter Elanor on our longer trails, several of which she had never hiked, before she and her parents set off for new lives in Arizona. I didn’t want her to forget the green lushness of a Pennsylvania summer. On one such walk, several almost grown turkey poults flew up in front of us. On another I pointed out blooming rhododendron, wild hydrangea, wood nettle and black cohosh along the road.

But Elanor was most impressed by the abundance of baby cottontail rabbits and adults in our yard, especially one attracted to our veranda. In fact, its cement floor proved to be alluring to a variety of small mammals including chipmunks that seemed affronted by Bruce and my sedentary presence on the veranda.

A long-tailed weasel

A long-tailed weasel (Photo by Bryant Olsen on Flickr, Creative Commons license)

We grew accustomed to sitting on our veranda chairs without speaking or moving as rabbits and chipmunks crept closer and closer. One morning, after I returned from my walk at 6:30, we sat there silently gazing at First Field. A long-tailed weasel emerged from beneath a forsythia bush next to the veranda and started toward the chipmunk burrow in the lawn at the far end of the veranda. When I turned to Bruce to see if he noticed the weasel, it dashed back the way it had come.

We remained silent, and a few seconds later, it ran on to the end of the veranda. Again I turned to Bruce and again the weasel retraced its steps. This time it didn’t come back. Bruce didn’t see it either time, but I even glimpsed its white underparts the second time around. This happened the day after my birthday, and I was grateful for my belated gift of a brief moment with an elusive creature.

Four eastern phoebe chicks in their nest

Four eastern phoebe chicks in their nest (Photo by jeffreyw on Flickr, Creative Commons license)

On our front porch a pair of eastern phoebes had built their second nest. One early July evening, while Elanor was eating dinner with us on the porch, the four nestlings became four fledglings as one after the other flew over our heads chirping.

Even our back porch was attractive to wildlife. One night I left a planter of house plants I had washed out on the porch to dry. The next morning I found a hole dug in the dirt and muddy raccoon prints on the porch floor.

And of course we had our usual bear sightings. Early in the month our son Steve, driving up our road in the afternoon, had a young cub run in front of his car halfway up the mountain. Near the end of the month, as I reached the top of Sapsucker Ridge, I heard a crash from a tree and caught a glimpse of a bear running downslope toward the interstate.

These glimpses I have of the lives of wild animals and birds are often tantalizing and sometimes I can only guess at their intentions. But I did solve one mystery and its perpetrators.

Norway spruce cones, including one in the lower right on which part of the cone scales have been removed

Norway spruce cones, including one in the lower right on which part of the cone scales have been removed (Photo from the Plant Image Library in Flickr, Creative Commons license)

One hot, humid morning inside the Norway spruce grove, I noticed dozens of still-immature spruce cones that had been clipped from the tops of the tallest trees and stripped of their overlapping cone scales. The scales lay in golden-beige heaps at the base of the trees.

Never before had I seen this even though the trees have had mature cones for years. But the acorn crop had failed for two years and I suspected hungry gray squirrels were after the two seeds at the base of each scale. Fourteen days later I spotted a gray squirrel climbing up a cone-laden spruce tree, proving to my satisfaction that they were producing the piles and scatterings of diamond-shaped cone scales throughout the grove.

Later, I read in North American Tree Squirrels by Michael A. Steele and John L. Koprowski about a study they did in North Carolina of longleaf pine cones. They found that even though the cones of most conifers don’t fully mature until October, they are already nutritious by late July when squirrels sometimes have little else to eat. The North Carolina fox squirrels stripped the longleaf cones the same way our gray squirrels had stripped the Norway spruce cones, by starting at the bottom of a cone and rotating it like an ear of corn as it gnawed off one cone scale at a time.

At the end of the month, after a much-awaited rainstorm the previous evening, I walked Laurel Ridge Trail listening to the same but much quieter suite of singing birds—scarlet tanager, eastern wood-pewee, and red-eyed vireo. I picked up a bird’s nest lined with thin stems and plastered with lichens. The exquisite little nest had blown from a high tree branch in the storm and had been constructed by an eastern wood-pewee.

Later, as I approached our yard, I noticed a male American goldfinch crying on and on from our electric line. Then a large raptor lifted off a yard tree and landed on a low black walnut branch. It was an immature Cooper’s hawk still peering around in search of prey and providing a close look at the white streaks above its eyes and its reddish breast and belly.

As soon as the hawk flew off, the goldfinch was quiet, and a gray catbird and several other birds began calling as if giving an all-clear signal.

July may often be an uncomfortable month to be outside, but my many glimpses of wildlife make every sweaty, buggy walk worth the effort.

 

 

Food for Wildlife

After three lean years, our oak trees finally produced a bumper crop of acorns last September. Forewarned by hordes of blue jays screaming from the treetops as they plucked ripe acorns from the oaks, I had to be careful on our steep trails not to slide on the fallen nuts that were more hazardous than marbles.

grey squirrel

Grey squirrel eating an acorn (Juraj Patekar image on Flickr, Creative Commons license)

Still, not every section of forested Pennsylvania had a good acorn crop, despite predictions from folks that should know better. Dr. Marc Abrams, a forestry professor at Penn State says there’s “no way to predict it,” calling a heavy mast year “one of the amazing mysteries in nature that we still do not have a handle on.”

Dr. Warren G. Abrahamson, a Bucknell University professor who conducted a long term study of acorn production from 1969 to 1996 with Jim Layne of the Archbald Biological Station in Florida, agrees, although he says that “the production of acorns definitely is not forecasting but hind casting the weather.” In their September 2003 report of their work they claimed that the size of the acorn crop each year is partly controlled by precipitation which affects acorns during different stages of development in prior years.

Other experts think that the group behavior of masting trees called synchrony most likely depends in part on the temperature during pollination in late April or May. Since oaks are wind-pollinated, meaning the wind must transfer pollen from staminate (male) to pistillate (female) flowers, a period of rain might disrupt the process.

For instance, a cold, wet spring in 2012 affected red oak production in 2013 because all the oaks in the black oak group (those with pointed lobes on their leaves) take two years to mature. Those in the white oak group (those with smooth lobes on their leaves) take only a year and would be affected by a late spring frost during pollination.

Still others believe that synchrony occurs as a way to outsmart nut predators by producing more nuts than the predators can eat, ensuring that at least some nuts will grow into trees. But whatever the causes, it is cyclic and occurs every three to five years.

On our dry mountaintop we have mostly chestnut oaks with an occasional white oak in the white oak group. Deer prefer these tastier acorns and squirrels eat them almost immediately because they spoil more quickly than those in the black oak group, which include scrub, black, northern red, and scarlet oaks here. Those acorns the squirrels store.

hickory nut

Hickory nuts form 10 to 25 percent of a squirrel’s diet in a good year (image by Peppysis on Flickr, Creative Commons license)

Acorns are not the only hard mast fruit. Others include the squirrels’ favorite—hickories, especially pignut, mockernut, and shagbark—which consists of 10 to 25 % of their diets in a good year and ripen before acorns. But like oaks, as well as the other hard mast producers—American beeches and black walnuts—they are also wind-pollinated.

Hard mast is high in fat, carbohydrates, and protein and is important to at least 180 species of birds and animals in fall and winter, but since it is highly variable in production from year to year, wildlife must depend also on a wide variety of soft mast throughout spring, summer, and fall. These fleshy, perishable fruits high in sugar, vitamins, and carbohydrates include a wide variety of native trees, shrubs, and woody vine species.

Foresters and wildlife biologists, in fact, consider mast to be the woody plant fruits and browse of native trees, shrubs and vines even though the word mast comes from the Old English “maest” which meant the forest tree nuts on the ground that fattened domestic pigs and other animals.

A wide variety of soft mast allows many mammals and birds to survive the lean years of hard mast. Of course, there are always some nuts every year, but ever since the extinction of American chestnut trees which, because they were insect-pollinated and didn’t bloom until summer, reliably produced an excellent crop of nuts, wildlife has had to adjust to a feast or near famine hard mast situation.

Consequently, encouraging biologically diverse meadows and forests, stocked with native trees, shrubs, and woody vine species produces food for wildlife throughout the year. And diverse food leads to diverse wildlife, as we’ve discovered on our property.

Other examples of trees that are insect-pollinated and produce a huge number of seeds every year as well as foliage, twigs and bark are red and striped maples. Striped maple, also called moosewood or goosefoot, has fruit that matures in early fall and is eaten by ruffed grouse, rodents, and songbirds. In addition, it produces browse for deer and bark for rabbits and beaver.

Elk eat the buds, foliate, twigs and bark of red maple, songbirds gorge on the seeds, and squirrels and mice store them for winter.

Basswood is another insect-pollinated tree, producing seeds squirrels and chipmunks consume while deer and rabbits browse its foliage.

The best of the soft mass fruit is that of wild black cherry trees. It fruits abundantly every third or fourth year in August and is pollinated by solitary bees. Seventy bird species feed on the fruit including grouse and wild turkeys. Black bears, raccoons, foxes, rabbits, squirrels, chipmunks and mice relish the dark cherries.

witch-hazel fruit and flowers

Witch-hazel fruit and flowers (Image by Rodger Evans on Flickr, Creative Commons license)

The fruit of sassafras trees, which is high in fat, is eaten by turkeys, bobwhite quail, black bears, pileated woodpeckers and gray catbirds. Rabbits and deer browse its twigs, black bears like its stems and deer its leaves. Despite its popularity, we have many sassafras trees in our forest.

Common witch-hazel, which flowers in late fall, develops woody capsules the following spring and summer. Those capsules contain a pair of shiny, black hard-coated seeds that shoot out in autumn before the next flowering. But squirrels, turkeys, quail, and grouse go after them, especially if the acorn crop fails. Deer browse heavily on witch-hazel, but it persists in growing above the deer line here.

Common spicebush (my personal favorite) produces brilliant spicy red fruits eaten by grouse, pheasants, and quail. It also provides shoots for rabbits and browse for deer, but it too survives and thrives, especially in wet areas along our stream. Our son Dave has planted it as an attractive shrub in our yard and his.

Both red-berried elder, which blooms the same time as the invasive barberry, has red berries available for birds in June or early July, although it only lives on steep slopes here because deer are fond of its browse. Deer also like common elderberry. It blooms in late June or early July and hangs heavy with clusters of dark purple berries favored by birds and humans in late August.

White-throated sparrow with staghorn sumac fruit

White-throated sparrow with staghorn sumac fruit (Kelly Colgan Azar photo on Flickr, Creative Commons license)

Staghorn sumac is making a recovery on our property, living on the sunny edges of meadows and forests. Blooming in late June and early July, its greenish-yellow, fragrant flowers morph into bright red, cone-shaped clusters of fruit that last through the winter, providing food for squirrels, songbirds, grouse, pheasants, turkeys and quail. Deer and rabbits browse on this shrub as well.

Wild berries are a popular summer food. First come the lowbush blueberries as early as mid-June on our powerline right-of-way, followed by the huckleberries. Black bears are particularly fond of them, but so are songbirds, grouse, chipmunks, pheasants, and mice.

Black raspberries ripen in early July and blackberries in early August. Both are incredibly important fruit for songbirds, skunks, opossums, foxes, squirrels, chipmunks, and black bears, while rabbits like their cover and rabbits and deer browse on their stems. Of course, the wildlife must also compete with me, especially in the blackberry patches.

Opossum eating wild grapes

Opossum eating wild grapes (photo by pverdonk on Flickr, Creative Commons license)

Greenbrier of several species has bluish-black berries eaten by songbirds and gamebirds and deer browse them. They browse wild grapevines too, but wild grapes are among the most important and valuable food for wildlife including songbirds, gamebirds, foxes, skunks, raccoons, opossums, squirrels and deer. The vines provide winter shelter for animals and birds too. I remember one winter when the hard mast failed and deer spent the season among the grapevines of the Far Field thicket, yarding up like they do in northern New England.

My list of native trees, shrubs and vines could be greatly expanded. In other parts of Pennsylvania, particularly south of us, still other wildlife food, such as common papaws, are important. But diversity remains the key to providing abundant wildlife food, even in years when hard mast is scarce.

Winter Porkies

porcupine up a tree in a snowstorm

Porcupine in a snowstorm, below the Road to the Far Field

Deep winter and at last a good tracking snow had fallen. While I may puzzle over some tracks, there is no mistaking those of porcupines. They plow through the snow on their naked, flat, pigeon-toed feet like miniature bulldozers, and when the tracks freeze, deer, opossums and foxes use them as winter highways.

When we first moved to our central Pennsylvania mountaintop in 1971, seeing a porcupine was a rare occurrence, but over the last couple decades porcupine numbers on our square mile of property have proliferated. During several days in early January last winter I found abundant tracks and numerous porcupines along the trails and in a variety of trees. Tracks wandered into and out of our three-acre deer exclosure, in and around our Norway spruce grove, and along the Far Field Road. Porcupines sat high in trees beside our hollow road, on top of Sapsucker Ridge, down in Roseberry Hollow and near the top of a Norway spruce tree. The latter was snoozing as its quills whitened in the falling snow.

Without leaves on the trees I could see many debarked crown branches. On Dogwood Knoll I found tiny pieces of bark at the base of a large chestnut oak tree, a sign that a porcupine had been eating the inner bark of one of the favorite trees of some of our porcupines. They also like red oak and sugar maple. Because they prefer small branches near the tops of these trees, we rarely lose a hardwood tree to their winter gnawing.

A tree de-barked by a porcupine near the spruce grove

A tree de-barked by a porcupine near the spruce grove

But our Norway spruce grove is porcupine central in the winter. Like white spruce further north, Norway spruce is a favorite winter food for porcupines. In addition, it provides excellent protection from winter weather. Porcupines like hemlocks too, especially for protection, and they eat the needles and twigs but not the bark because it is too strong in tannins. Our hollow hemlocks used to be popular with porcupines in the deep winter, but as the hemlocks have thinned and, in some cases, died from the ravages of the hemlock wooly adelgids, porcupines, ever adaptable, have switched to other trees, most notably our Norway spruces.

Porcupine tracks led into the grove from Sapsucker Ridge and the Far Field Road. By late January numerous spruce trees bore fresh tooth marks from gnawing porcupines. Porcupines move slowly in the woods, just as I do, so they are easy for me to track. Unlike colder, northern places, where they are out mostly at night, here they are out and about both night and day. No doubt our porcupines were especially hungry last winter because the acorns, one of their favorite autumn foods, had failed for three years.

One day I surprised a porcupine sitting on the snow-covered Far Field Road. When I approached it, it stood up and slowly climbed a large sugar maple tree. Fifteen days later, in early February, I followed what may have been the same porcupine from the base of the spruce grove to the Far Field Road. The trail ended at the entrance to a hollow, fallen log below the road where a porcupine turned its back to me.

According to Uldis Roze, who has spent 24 years studying porcupines in the Catskill Mountains of New York state, porcupine fur has excellent insulating properties, which allows them to use hollow logs, trees, and rock crevices as winter dens. Usually they turn their backs to the den openings, sit with their bodies propped up by their tails, and hold their front paws against their chests. They turn their hind paws sideways so their naked foot pads don’t touch the ground. When resting in high trees, they roll up into balls and can withstand extremely cold temperatures. No wonder they are able to live as far north as northern Alaska, Quebec, and Labrador, in fact, at or beyond the tundra line.

A young porcupine in deep snow by Martin Male

A young porcupine in deep snow (photo by Martin Male, CC licence)

By mid-February, the so-called “polar vortex” was not only dropping our thermometer to as low as ten degrees below zero on some days, but it began to snow in earnest. And again I found the same porcupine tucked into the hollow log along the Far Field Road, its back white with snow.

With 18 inches of snow on the ground, I broke out my snowshoes and headed up to the spruce grove. As I broke trail around the grove, I saw fresh porcupine tracks and then spotted a porcupine at the base of a spruce tree. It started up the tree when it realized I had seen it, but it didn’t climb more than a few feet before it went around to the back of the trunk as if once out of sight, I would forget it was there. Then I noticed a circle from its body at the base of the tree as well as a pile of cylindrical, gray and/or brown, inch to an inch-and-a-half-long porcupine scat (droppings). It must have been there for some time.

I also broke trail along the Far Field Road and encountered the porcupine in the same hollow log after a night of stripping bark from the lower spruce grove trees, just as the one I saw earlier specialized in the upper part of the grove.

Every time I passed the Far Field Road hollow log for most of February, the porcupine was either in the log or plodding its way back to it. And then tragedy struck. On February 27 I found a dead porcupine behind the spruce grove, still clinging to the thin branch of a black locust tree. Apparently, it had fallen from the large spruce it was gnawing and had broken the locust branch off on its way to the ground. Probably it had died sometime after it had hit the icy snow since there were puddles of urine around it.

Remains of the dead porcupine in the spruce grove, 7 months later

Remains of the dead porcupine in the spruce grove, seven months later

Roze says, in his book The North American Porcupine, that porcupines risk injury and death from falling out of trees because they are relatively heavy and prefer to feed far out on branches that are often brittle. I know I’ve watched them foraging on hardwood tree branches, expecting them to fall any moment as they crawl farther and farther out on a limb that bends with their weight. Sometimes porcupines do fall, but they are usually badly hurt. For instance, one of Roze’s study animals had a series of injuries that he called “consistent with falling belly-first out of a tree.”

According to Roze, another researcher, Wendell Dodge in western Massachusetts, who autopsied 200 porcupines back in 1961, found healed leg, hip, and rib fractures, broken teeth, injured eyes and ears, hernias, and soft-tissue injuries. One even had a four-inch-long pine branch in its abdomen.

A week later, in early March, I checked on the dead porcupine and found a live one sitting next to it on the ground under the large spruce tree almost as if it was holding a late wake for it. Eventually it shuffled over to the spruce trunk, deftly climbed its mostly bark-stripped trunk, and moved far out on the limb.

I followed other porcupine tracks from the upper section of the grove over to the neighbor’s clearcut on Sapsucker Ridge. There I saw a small but old chestnut oak and a bent, larger one, both of which had debarked branches. Beneath them were bark pieces and scat littering the ground. I continued following the tracks for 20 feet to the remains of a hollow tree log left by the loggers. At its entrance was a huge pile of porcupine scat. I knelt down on the snow and peered inside the log. A porcupine was tucked into it.

Both log dens were 200 feet or so from the spruce grove. While porcupines wander much greater distances during the summer, their temporary winter dens, which they use for an average of 23 days, are usually within 300 feet of their food trees. The spruce grove porcupines followed that pattern.

A porcupine in one of the hemlock trees down in the hollow

A porcupine in one of the hemlock trees down in the hollow

The same porcupine appeared three days later at the base of the large spruce where the other porcupine had died and reluctantly climbed the tree when I spoke to it. It looked as if that beautiful tree had been completely girdled high up. So too had at least four other large spruces. But according to Gary Gillmore, a state forester, Norway spruces throw out new limbs if they have been topped.

By March 10 I was seeing as many as four porcupines feeding in our hollow hemlock trees, leaving nipped twigs and scat on our road. Although this was still winter food, probably they had left dens upslope early and were using hemlock habitat for shelter, meager though it was.

Near the end of March, I found only two porcupines in hardwood trees and they were eating buds. The rest seemed to have disappeared once spring arrived. But I had enjoyed my porcupine winter and the chance to learn a little about how they survive the cold months.


All photos taken on the mountain by Dave Bonta, except where indicated.

The Value of Aging Trees

A big red oak on top of Sapsucker Ridge

A big red oak on top of Sapsucker Ridge

On a hot July day, I sit beneath a large red oak, nestled into a deep buttress, one of several that flare out from this 200-year-old tree. The ground beneath the tree is littered with old acorn remnants as are the bases of the other elders in this stand of deciduous trees.

Protected as a picnic spot by the previous owners, the trees were allowed to prosper even as other portions of our property were cut over in the nineteenth and even twentieth centuries. Instead of fencing a young forest, such as that last 120-acre cutover piece we acquired back in the 1990s, we put up our three-acre deer exclosure in March 2001 around these mature trees.

Now, as I gaze around, I see dozens of oak seedlings and saplings filling in the forest floor. Most are red oaks, but some are offspring of the enormous white oak beside the exclosure gate.

Technically, this is not an old-growth forest but one that is becoming old-growth. Still, it and much of the rest of our property consists of an aging forest. Not long ago, old trees were seen as useless and were harvested so that young trees would grow in their place. But in the last few decades scientists have been discovering that old trees in an old forest are incredible absorbers of carbon dioxide. And red oaks, with their dense wood, are particularly good at absorbing impressive amounts of carbon.

One study, in Massachusetts’s Harvard Forest, found that at 50 years of age, their trees, both oak and maple, were absorbing 0.8 tons of carbon per acre every year. After 15 years, the rate of carbon uptake had doubled. Researchers studying old-growth forests in the West discovered that those forests too absorbed more carbon as they aged.

One of those researchers, Bev Law, of Oregon State University, told a journalist that, “Across forest types, globally, we find that the amount of carbon stored is high in older forests, and that live carbon continues to accumulate for centuries.” This carbon is held not only in the trees themselves but in their fallen leaves and branches as well as in the fertile soil of old forests.

Law is director of the AmeriFlux Network, an international collaborative project founded in 1996 to measure the carbon dioxide, water vapor, and energy in all kinds of major ecological community types or biomes in North, Central, and South America. Using a variety of sophisticated tools, scientists are able to track carbon in any ecosystem. Here in our eastern forests, studies have been done in several states including the aforementioned Massachusetts.

Old trees in an old forest have other uses too. They provide large hollow trees for a variety of birds and animals that use them for nesting, food, and shelter. For instance, sycamore trees are the most massive trees in the eastern United States. They can grow over 100 feet tall and 10 feet wide and live up to 500 years. When they are very old, they have a cavity at ground level large enough, in one recent case, to house a maternity colony of 100 Indiana bats, researchers discovered back in 1993.

A giant eastern hemlock tree in Central Pennsylvania

A giant eastern hemlock tree in Central Pennsylvania

Large, hollow trees also appeal to children of a certain age. I was reminded of Jean Craighead George’s book My Side of the Mountain which my husband Bruce read aloud to all of us when our three sons were young. They were all entranced by the 12-year-old hero of the story, Sam Gribley’s large, hollow tree home in the wilds of the Catskill Mountains. In his case it was a hemlock tree. Remembering the many old-growth hemlocks we have (or had, before the hemlock woolly adelgids killed so many of them in our Pennsylvania old-growth forests), I knew that such trees might have been large enough to house one young boy.

Because our old-growth hemlock trees are mostly in Pennsylvania’s state natural areas, the trees attacked by adelgids have been allowed to die and be reclaimed by the earth as our son, Dave discovered during a recent visit to Snyder-Middleswarth Natural Area. Many people find this wasteful, believing that such trees should be harvested. But Dr. Joan Maloof, who has been writing and speaking about the value of old-growth forests, maintains that “old-growth forests are one of the few land uses where topsoil is created instead of destroyed.”

We like to think that our own younger but mature forest is also creating soil as we allow our trees to fall over and rot, creating, as our young nephew Patrick once cried over and over, “Dirt, dirt, dirt” while sifting the powdery, reddish-brown remains of red oak branches through his fingers. Those powdery remains of the heartwood and sapwood appear to be a nursery for the downy rattlesnake plantains I’ve discovered inside and outside our exclosure. When we first put up the exclosure, I found a large colony of this orchid growing on a slope where several trees had rotted down to heartwood and sapwood. Another plant that we found outside the exclosure and fenced had germinated beneath a stump that was seeping rotted wood at its base.

Then, a couple years ago, I found still another downy rattlesnake plantain plant that had germinated on the decaying remains of a fallen red oak limb. At the same time, I noticed that the fenced plant outside the exclosure was looking poorly. I gathered up more of the “natural” fertilizer from the trunk and sprinkled it over the plant, and once again it is thriving. I haven’t seen any studies that indicate that downy rattlesnake plantain needs this material, but I wonder.

Photographing downy rattlesnake plantain in our deer exclosure

Photographing downy rattlesnake plantain in our deer exclosure

As our forest has aged over the last 41 years we’ve lived here and now nearing one hundred years of age in our hollow area, our forest bird diversity has increased. Fallen trees across our first-order, headwater stream, attract several breeding Louisiana waterthrushes and winter wrens. Barred owls court and nest in our larger, hollow trees. Scarlet tanagers, worm-eating warblers, and red-eyed vireos, among others, are more common than ever. Once we had no nesting black-throated green warblers, cerulean warblers, blue-headed vireos, winter wrens, or Acadian flycatchers, but our aging forest has attracted them. All of these bird species and several more, such as blackburnian warblers — depending on whether species need coniferous, deciduous or mixed deciduous forests — use older, mature forests. And the larger these forests are, the better the chances are for the birds to fledge nestlings.

The same is true for many mammal species. Bears, raccoons, and porcupines, for example, like to den in large, hollow trees. One study of black bear den trees found that in order for red and white oak trees to be big enough, they had to be between 175 and 280 years old, which reminds me of the huge oaks our boys found more than 30 years ago at the steep base of our mountain on a property line with a neighbor. They took some box camera photos of themselves standing in front of them and they looked as if they were as large as California redwood trees. I was amazed and delighted, but before I had a chance to see those trees, our neighbor’s logging operation had cut them down. The boys went to check on them and said that they were all hollow inside, so excellent habitat had been destroyed and not a dollar earned on those trees.

The same den tree study found that raccoons liked tree hollows in trees from 90 to 164 years old, and gray squirrels 65 to 130 years in age. Many bat species, too, like old trees with cavities and loose bark. Other opportunities for denning in older forests include in soil pits created by large root masses of wind-tilted trees, in the root masses themselves, and in stumps, logs, large, horizontal limbs and cavities in standing trees, all of which we have in abundance in our aging forest..

One special kind of older forest that has diminished greatly is that of mixed red spruce and hemlock in the northern tier of Pennsylvania. Such a forest especially appeals to red-backed voles, water shrews, and state-endangered northern flying squirrels. According to researcher Dr. Carolyn Mahan of Penn State, this type of coniferous forest creates a moist microclimate that supports a diversity of fungi, which both the voles and the northern flying squirrels thrive on. They also spread the fungi spores, thereby enriching the soil. Water shrews also seem to prefer such forests, but they like them to be in swampy ravines.

Megalodacne heros beetles feed and mate on varnish shelf fungi, found on an ancient hemlock logs

Megalodacne heros beetles feed and mate on varnish shelf fungi, found on ancient hemlock logs

We also have red-backed voles in our deciduous forest, and Mahan explains that they are not specific to old red spruce/hemlock forests, but more of them are found there than in forests such as ours. Northern flying squirrels are much rarer in our state because they are habitat specialists and their red spruce/hemlock forests have been lost to habitat fragmentation from development of all kinds and to hemlock woolly adelgids. The remaining smaller, patchier coniferous groves next to deciduous forests also attract the more generalist and numerous southern flying squirrels. They are sharing nest sites and even hybridizing with northern flying squirrels, and in the process, passing on a roundworm species, Strongyloides robustus, to which they seem to be immune but which is killing the northern flying squirrels.

Mahan has 600 nest boxes in 21 study sites for the northern flying squirrel, and this year not one northern flying squirrel has been found in any of those boxes. Last year she and other researchers planted an experimental 2500 native red spruce seedlings among the dying hemlocks of a site and others in a recent Game Commission clearcut which was fenced to see if they will grow and thrive and someday produce more red spruce forests. If they do well, they will plant more red spruce seedlings. But think how long it will be before there will be another red spruce forest as magnificent of those we had in Pennsylvania. How much better it would have been if we had saved larger pieces of our older spruce forests.

After talking to Mahan and other researchers, I am more determined than ever to keep growing an older forest. But on this hot summer day, I most appreciate our mature forest for its deep shade that cools not only me but all the creatures large and small that live here.

All photos by Dave Bonta ~ click on images to view larger versions at Flickr