Karst Landforms and Sinking Creeks

Every time I drive South Buffalo Road near my home, I pass by a completely dry creek bed. The width and depth of the creek bed is evidence that a fairly big creek once ran through here. The deep channel, cut by hundreds of thousands of gallons of water passing through each day, eroded the soil and exposed the rocks left behind.
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Along this same road I also noticed several large, circular depressions, which I learned are sinkholes. The sinkhole pictured below is only about 12 feet deep, but since I became aware that our area is filled with sinkholes, I have seen some much deeper. Sometimes their true depth is not known because the “bottom” is obscured by vines and tree limbs.

sink hole2

This sinkhole, in  the middle of a grassy field, was formed a long time ago because the trees grew out of the hole once the area could no longer be mowed.

I did some research and found out that sink holes and “disappearing creeks” have a connection. The Ridge and Valley Province of the Blue Ridge where we live has a type of topography known as “karst.” Karst terrain is characterized by springs, caves, sinkholes, disappearing streams, and a unique hydrogeology that results in highly productive aquifers.

Karst terrain is largely supported by rocks such as limestone or dolomite that are highly porous and broken down by water. As water from streams or rainfall dissolves the bedrock, fractures occur. Over time, these fractures are enlarged and an underground drainage system begins to develop, allowing more and more water to pass through the system. Eventually, large hollow areas can be carved out underground and these unstable areas become vulnerable to earthquakes, construction, groundwater pumping, hurricanes, or other forces, which can cause cave-ins, or sink holes.

How a karst sinkhole is formed. Illustration by Denise Dahn (www.dahndesign.com/denises-blog/) for an interpretive sign at the Tongass National Forest in Alaska.

How a karst sinkhole is formed. Illustration by Denise Dahn (www.dahndesign.com/denises-blog/) for an interpretive sign at the Tongass National Forest in Alaska.

This sinkhole in Frederick, MD opened up in 2003. Many sinkholes occur along highways where rainwater runoff is concentrated into storm drains and ditches increasing the rate of sinkhole development (note the sewer drain pipe beneath roadway). Photo by U.S. Geological Survey.

This sinkhole in Frederick, MD opened up in 2003. Many sinkholes occur along highways where rainwater runoff is concentrated into storm drains and ditches increasing the rate of sinkhole development (note the sewer drain pipe beneath roadway). Photo by U.S. Geological Survey.

Streams that begin as runoff from mountain slopes often disappear into the subsurface when the water comes into contact with karst bedrock. These disappearing streams are called “sinking streams.” The water flows underground, emerging as a spring somewhere along the valley floor, sometimes miles away from where it plunged underground.

How water flows through karst bedrock. Illustration by Denise Dahn (www.dahndesign.com/denises-blog/).

How water flows through karst bedrock. Illustration by Denise Dahn (www.dahndesign.com/denises-blog/).

What all this means is that the creek I saw didn’t dry up – it’s what’s called a “sinking stream.” At some point along its course, the creek dropped through a fissure in the underlying rock and now flows underground. Because much of a karst watershed can be hidden underground, it’s hard to track exactly where water comes from and where it goes. I’m fascinated by the karst topography of the Blue Ridge, which means another post on this subject sometime in the future.

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Spring Jewel: The Eastern Redbud

Spring has officially arrived in central Virginia! Our native Eastern Redbud trees (Cercis Canadensis) have awakened from their winter slumber and are in full bloom. Redbuds reach their flowering peak when most shade trees are just beginning to leaf-out, so this time of year their brilliant sprays of pink jump out at you along the highways and back roads. The flowers almost glow against the lime green shade of new deciduous leaves and the dark green tones of neighboring evergreens.

Redbud trees peeking out from the woods

Redbud trees peeking out from the woods

The Eastern Redbud is native to the Blue Ridge and much of the Eastern U.S. Growing in moist, well-drained soils, frequently along woodland edges, they can reach 20 to 30 feet and six to 10 inches in diameter. In early spring, before the leaves form, bright pink to purple flowers, one-half inch long, appear in clusters along the twigs and small branches.

Eastern Redbud
A couple of weeks later, tiny leaves appear at the tips of the branches, signaling the end of the flower show. The dark green leaves are large and heart-shaped. Once the tree has leafed-out and the flowers have faded, large brown seed pods, two to four inches in length, will form. The seeds inside, which are brown and about a quarter of an inch long, will be mature before the end of summer and can be planted in the fall. Any seed with a hard outer coating like the redbud will need to be scarified (sanded or nicked) so water will reach the seed to cause germination.

Due to their manageable size, redbuds are a popular landscaping tree. As a member of the legume family, redbud roots are able to convert nitrogen from the air into a form plants can use, so this tree can grow in poor soil and can actually improve the soil in which it grows.

I was amazed when I looked at the date of the first picture in this post. It was taken on March 24, 2012, a full three weeks earlier than the second picture taken on April 15, 2013! I knew winter was slow to arrive in Virginia – this confirms just how slow.

Coyote in the field

I have a habit of looking out the window a lot during the day, wondering what I’m missing while I’m inside. This morning, I happened to look out and saw a dog-like form in my neighbor’s field. Even though it was a football field away, the animal’s size and gray/tan coloring told me it was an Eastern Coyote. I grabbed the binoculars and sure enough, it was a large coyote. Extremely wary, coyotes don’t stay in one place for long. By the time I found my camera, he had moved behind a hill and out of sight.

I hurriedly put on my coat and went out to have a look, but by the time I got to where I had seen him, he was gone. Our neighbor’s farm is 300 acres of woods and fields, with lots of places where a coyote could hide or raise a family. Coyote breeding season is underway, so if he has a mate and pups nearby, I might get to see him again.

Coyotes move through our area, but haven't caused any problems. Photo by US Fish and Widlife

Photo by U.S. Fish and Wildlife Service

Coyotes make their dens in a burrow under rocks, in hollow tree trunks, and under piles of brush. If undisturbed, they will repair and use the same den in successive years. Females produce a litter of three to 12 pups which are born between March and May. The male and female both engage in hunting rabbits, mice, wild turkeys, deer, rodents, and other food sources.

The pups begin to venture outside the den at three to four weeks of age. (To see pups emerging from their den for the first time, watch this wonderful video called “Coyote Cubs Singing” produced by BBC Worldwide.) Young coyotes will leave their parents care in the fall following their birth. If food is abundant, the pups will stay and hunt in the family pack until the start of the next breeding season. If food is scarce, they will leave to find their own hunting territory. Overall prey abundance and diversity dictates the total number of coyotes that can thrive in a given area. (source: Virginia Department of Game and Inland Fisheries.)

Historically, the coyote was commonly found in the Great Plains of western and mid-western states, but during the last 50 years has expanded its range eastward. Two factors that contributed to the eastern expansion were the elimination of its ancient foe, the timber wolf, and the establishment of the deer herd in the East as a plentiful food base. The coyote is an adaptable and resourceful predator and despite efforts to reduce their numbers in many places, there may be more coyotes today than in colonial times.

In the Blue Ridge, coyote populations are increasing, largely due to abundant small prey and deer populations. These cagey predators tend to steer clear of humans, but will take livestock such as chickens, sheep, pigs, or domestic animals if the opportunity presents itself. We do have to be concerned about our chickens and I worry about Callie, a Shih Tzu-mix of about 20 pounds, so we keep a close eye on her when she’s out. Supposedly, they do not particularly target livestock or domestic animals, but if the pickins’ are easy….

In the meantime, I’ll keep looking out the window.

In Search of Spring

Although our winter here in the Blue Ridge has actually been pretty mild, I find myself longing to see green fields and hillsides once again. With only a few weeks of winter remaining, I set out to look for signs that winter is loosening its grip on the land and giving way to the season of renewal. My last walk was several days ago and I was amazed at how much the landscape had changed.

The growing moss pays no heed to the frigid temps of the water

The growing moss pays no heed to the frigid temps of South Buffalo Creek

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Another type of moss growing up through the leaves

Immature cones forming on terminal ends of Virginia Pine

Immature cones forming on Virginia Pine

Still another kind of moss

Still another kind of moss

The birds are also giving clues that spring is on its way. The Eastern Phoebes can be heard issuing their phoebe, phoebe calls as they check out our porch rafters for the choicest nest sites. I’m also seeing the Eastern Bluebirds once again that had retreated to lower elevations to escape the worst of winter, and a Northern Mockingbird pair is busy chasing intruders out of their favorite tangle of vines.

Although the nights are cold, it’s the breeding season for many animals. Last night, my husband and I were awakened by the shrill cries of a fox in the front yard. The cries, a little higher-pitched than a coyote, went on for about a minute. My first thought was of the chickens, but I knew they were safely locked up in the coop. Possibly, the fox was calling to attract a mate. 

The lengthening of the days is obvious to our hens, who have started laying again, so it’s just a matter of time until winter blows its last gasp. I just need to be patient.

There is a way that Nature speaks, that land speaks. Most of the time we are not patient enough, quiet enough, to pay attention to the story. — Linda Hogan

The more we learn about crows, the smarter they get!

A  few years back, I wrote an article for Washingtonian magazine about wildlife to be found in urban areas, even a large metropolis like Washington, DC. In it, I made a casual reference to the “smart crow” scavenging for food in a McDonald’s parking lot. I couldn’t believe it when the editor omitted the word “smart” in the published article – maybe he thought readers would get confused, thinking I meant smart like Albert Einstein!  I guess I shouldn’t have assumed that everyone had heard of the intelligence of the corvid family, which includes crows, ravens, rooks, jays, jackdaws, and magpies.

Always watching and learning, crows are very resourceful. They can mimic calls of other birds, make tools, play tricks on each other, recognize and communicate danger to flock mates, and talk to each other in a dialect all their own. Their personality and ingenuity make them a fascinating group to watch. In all animal groups, brain size increases with body weight. The corvid’s brain is larger than other birds relative to its size – more in line with primates – when graphed against its body mass. This undoubtedly figures into what many researchers consider the bird’s intelligence in getting along in the world.

Most of the year, crows travel in tightly-knit family groups where they work cooperatively to find and exploit food sources. Photo by Lisa Rest at musicbirdblog.com.

Most of the year, crows travel in tightly-knit family groups where they work cooperatively to find and exploit food resources. Photo by Lisa Rest at musicbirdblog.com

Generally too cautious to come to feeders, crows will often congregate in large numbers to glean farm fields, but they have also developed some pretty unique ways to get food. My husband and I took a picnic lunch up to the Blue Ridge Parkway one day and while we were eating, we watched two crows dropping walnuts onto the hard road surface to crack them open. Then they would fly down to inspect the shells and clean out the nut meats. I’ve heard that crows will also place hard-to-crack nuts on roads in front of passing vehicles and then retrieve the crushed pieces. Maybe someone else has witnessed this, but I haven’t.

Some crows are known to be tool users in their natural environment. The New Caledonian Crow has been intensively studied recently because of its unique ability to manufacture and use its own tools in the day-to-day search for food. These tools include breaking off twigs and using torn leaves with barbed edges as hook-tools to dislodge insects from holes and crevices.

Crow using a stick as a tool. Photo by sciencemag.com

Crow using a stick as a tool. Photo by sciencemag.com

Scientists from New Zealand’s University of Auckland wanted to find out if New Caledonian Crows could spontaneously make tools from materials not previously encountered in order to get food. Placed in a situation where the bird can reach but not obtain a morsel of food using a straight piece of wire, it will bend one end of the wire into a hook. It then uses the hooked end to reach and obtain the food. The researchers believe that there is cultural evolution going on with the New Caledonian crows; that is, they invent new tools, modify existing tools, and pass these innovations to other individuals in their group.

As a young girl, I watched and listened to the crows communicating with each other. I decided the “crow call” was the perfect way to secretly communicate with one of my tomboy friends. While playing in the abandoned orchard behind our neighborhood, the “caw-caw” let us “talk” in a language no one else could decipher. I felt very clever using our secret crow calls. We were, after all, being sly and trickster-ish, mimicking what we understood to be a very intelligent bird.

If only we’d known back then what would come to light about crow intelligence years later, we’d have reveled in our secret crow calls even more. There’s a lot more going on in the corvid brain than we ever could have imagined.

“The important thing is to not stop questioning. Curiosity has its own reason for existing.” ~ Albert Einstein

Morning walk and signs of spring

Even though it looked like a storm was brewing in the distance, Bill and I took advantage of the warmer temps to go for a morning walk.

view of Short Hills

View of our neighbor’s barn further down the valley with the Short Hills in the distance

clouds over mountains

Clouds hanging over Garden Mountain

Walking along the edge of the woods, I was able to get this photo of a male cardinal that watched us curiously from a distance. The beauty of these exquisite birds is even more evident when seen in stark contrast against the bare limbs of the trees on a gray day like today.

Male northern cardinal

With the lengthening days, subtle changes are taking place everywhere. Wearying of winter, I was looking for signs that spring is on its way. The first thing I noticed was the swelling buds on the trees. As the days become warmer, the trees take up water in order to swell the buds and get the leaf-making process underway for the new growing season. The swelling is caused by the pressure of the sap pushing its way to the limb’s extremities.

buds on tree limbs

The buds on the tulip poplars are swelling, and I also noticed that the seed cones have opened and dropped most of their seeds. The viable ones will germinate once the ground warms up enough.

Tulip flowers

On the way back, I saw one of my favorite birds, a White-breasted Nuthatch. This dapper guy didn’t mind pausing his search for insects long enough to pose while I snapped a picture. Despite its wide distribution throughout North America, little is known about the specie’s breeding biology, in part, because they prefer to breed in natural holes in large, old trees, so their nests are often difficult to examine.

white-breasted nuthatch

I came back from the walk feeling encouraged about the signs of spring. All in all, it hasn’t been a bad winter; still, I long for the sounds of birds singing in the morning, the warmth of the sun, and all the wondrous activity of the season of renewal.

“Winter is on my head, but eternal spring is in my heart.”
Victor Hugo

Living with Nature in the Blue Ridge: 1st Anniversary

It’s hard to believe a whole year has gone by since I started “Wood and Field,” and what an incredible year it’s been! Thanks to the miracle that is the Internet, I’ve made many blogging friends who have shared what’s happening in their woods and fields – as far away as Finland! I remember how excited I was to get my first follower (okay, it was my husband, but you have to start somewhere, right?). Then I got more followers and the comments started to come in, and from then on, I was hooked!

I thought a lot about what I’ve learned over the past year. The first thing that came to mind is that storms in the mountains can come on fast and furious as temperatures fluctuate. I once exclaimed to my husband in exasperation after several weeks of high winds, an ice storm, a tornado, and torrential downpours that transformed the front field into a river and swept away parts of our gravel lane, “How come we don’t ever get any regular weather?”) What I’ve learned is that when you live in the mountains, changes in the weather can be sudden and severe.

a wild South Buffalo Creek during a big storm

a wild South Buffalo Creek during a big storm

The harsh turns in the weather have made me admire the resilience of wildlife all the more. The plants and animals that call the hills and valleys of the Blue Ridge home have evolved to cope with whatever nature throws at them. The lesson for me? I have to adapt, as well. I need to be more like the animals that carry out their routine despite adversity and remember that, eventually, normalcy will return. Of course, we might need to bring in a backhoe when that happens.

I’ve learned to watch the bird activity at the feeders for signs of significant changes in the weather. A special middle-ear receptor called the Vitali organ, can sense changes in barometric pressure. When I see the birds jockeying for position at the feeders and more gathered on the ground and in the trees, I know it’s time to get out the batteries and candles because Mother Nature is on a tear again!

Dozens of birds

Fueling up for a long winter’s night.

Another lesson I’ve learned is that although we share our space with coyotes, bears, and bobcats, we can co-exist in peace. I have to admit the first time I heard the high-pitched “yipping” of coyotes in the woods, a chill went up my spine, mostly because I didn’t know what to expect. We hear them from time to time early in the morning or at dusk, but they cover a wide territory and eventually move on. We seem to have reached an agreement that they leave us alone and we leave them alone.

Coyotes move in and out of our area, but haven't caused any problems. Photo by US Fish and Wildlife

Coyotes move in and out of our area, but haven’t caused any problems. Photo by US Fish and Wildlife

Finally, it’s been six years since we stopped mowing the fields and the regeneration is incredible. What used to be a hay field is now full of native grasses, wildflowers, shrubs, and tree saplings. We saw an American Kestrel for the first time this year on the farm, a species that is on the decline in Virginia. The kestrel and other birds of prey benefit directly from the overgrown fields that provide habitat for mice, voles, and other small animals.

I am looking forward to sharing many more vignettes of what’s happening in the natural world as I begin my second year of “Living with Nature in the Blue Ridge.”