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Of Fruit and Flowers

February 4, 2011

These are the dog days of summer…in the southern hemisphere. We need a winter equivalent here to signify these short, cold, and above all, very gray days as the calendar flips from January to February.

One thing that characterizes these mid-winter days for me is that monochromatic tedium of gray: gray branches etched against gray skies. At this point, birds have stripped away the fruit from dogwoods, cedars, hawthorns, and crabapples. Even the fruit of introduced plants such as honeysuckles, buckthorns, and Asiatic bittersweet – so abundant in urban areas – is for the most part long gone.

Just about the only splash of vegetative color is the red hanging clusters of fruit from the highbush cranberry, Viburnum opulus. (The taxonomy is a little tortured – V. opulus is the introduced European shrub, while the native variety is sometimes known as V. trilobum. They’re now usually considered subspecies; in much of the northeast you might find one, the other, or hybrids.) Although it gets picked at occasionally by birds after it ripens in fall, most highbush cranberry fruit isn’t consumed by birds until early spring.

I had always heard the fruit on highbush cranberry remains all winter because it didn’t “taste good” to birds until it had frozen and thawed multiple times. In fact, studies with captive American Robins and Cedar Waxwings determined that they preferred fall fruit in side-by-side trials. Sugars in highbush cranberry fruit do concentrate over the winter due to dehydration, but the chemical composition remains the same, and songbirds, in any case, don’t have much of a sense of taste.

The real reason birds don’t eat highbush cranberry fruit until spring is a little more complicated. The fruits are very acid and low in nitrogen. Birds need a supplemental source of protein to properly metabolize highbush cranberry fruits. In early spring, this protein source is often pollen, in the form of the insignificant-looking flowers of trees like cottonwoods, maples, and oaks.

This is a pretty clever strategy on the part of the Viburnum. In the fall when the fruit ripens, there is a whole smorgasbord of other fruit for birds to choose from. By retaining fruit until spring, highbush cranberry reduces the competition, and hones in on a very efficient seed disperser: the Cedar Waxwing (or in Europe, Bohemian Waxwing). In spring, at a time when many other bird species are beginning to rely on insects for food, waxwings remain mostly dependent on fruit, and highbush cranberry has set the table.

When a flock descends on a patch of highbush cranberry shrubs and goes to town on the fruit, you might also note that they make frequent forays into neighboring trees to partake in a little meal of pollen, completing their dietary requirement. As is their habit, waxwings wipe out a patch of berries and then go on their nomadic way, distributing Viburnum seeds far and wide, just as nature planned it.


Bark Ages

February 3, 2011

The stark winter forest has me looking closely at tree bark. Identifying trees by bark texture takes some practice. Like all of us, bark ages.

But first, a bark primer and reminder. Underneath that outer bark I have been looking at is, well, the inner bark. Technically called the phloem, this acts like a pipeline for leaves to pass food to the rest of the tree. Between the bark and the actual wood of the tree is a thin layer, really only one cell thick, called the cambium. Auxins are hormones that are produced each spring in leaf buds. These hormones travel to the cambium layer via the phloem and tell the cells to produce a little bit of new bark on one side and often a lot of wood on the other, the annual rings.

Outer bark has many functions. It helps to prevent water loss through evaporation, protects against attacks by insects and disease, insulates the tree from temperature swings, and in some species protects it from fast moving fires.

Each tree species outer bark has patterns that are often distinct and are a great aid for tree identification. The outer bark cells are dead and hardened and as trees grow and expand, the outer bark stretches and tightens. Eventually the pressure causes it to split, crack or flake. Add a little damage from rain, ice, wind and snow and you can find a lot of variability in bark. Understanding how bark ages and changes can help you better identify trees.

Take our iconic tree of New England, the Sugar Maple. Young trunks have bark that is relatively smooth and gray colored. As the tree ages the bark begins to fissure in long irregular flakes. When it is really old it becomes thick, dark and deeply furrowed. Each bark age gives the appearance that you are looking at a completely different tree species.

Black Cherry bark changes dramatically as it ages. Young trees have thin bark with narrow lenticels, corky pores that allow direct gas exchange. As the tree grows the bark remains smooth like a young birch tree. But as the tree grows old the bark becomes dark charcoal colored and very flaky.

Leaning trees or sides of trunks exposed to more severe weather conditions can be abnormally smooth even when a tree is old. The fissures and furrows in the bark catch and hold rain, snow and ice. The bark foliates from the action of freeze-thaw cycles creating a smoother appearance. Wind blown snow can also be abrasive and create smoother than normal bark on older trees.

Severe cold spells followed by rapid warming can cause trees to split. These are called frost cracks. Apparently, late growth stimulated by warm fall temperatures, high humidity, and high nitrogen levels can cause a tree to be more susceptible to frost cracks. The crack usually begins internally, but may expand with freeze-thaw cycles eventually splitting the bark. Such cracks are an opening for disease and insects to attack, sometimes killing the tree.

During the winter the sun is low on the horizon in the north woods. The air temperature during the afternoon may only read 10 degrees Fahrenheit on your thermometer. But on a clear winter day, the sun’s rays strike more directly on the trunks of trees. Light colored bark reflects the sun and keeps the tree from acting like a solar panel and heating the interior trunk well above freezing. The rapid expansion and contraction caused by extreme temperature changes can cause the tree to crack.

But smooth bark on some tree species may be an adaptation for protection too. A load of dark-colored epiphytes on a light colored trunk can cause the tree to become even more overheated. Smooth bark is harder for epiphytes, like lichens and moss, to cling and grow. Some species, like Paper Birch, not only have smooth, white bark, but they also peel, which constantly sheds the epiphytes and other debris keeping the trunk clean and white.

Bark can tell us a lot about tree identification and ecology. On your next walk in the woods, check out the bark ages.

Winter Forage for Wild Turkeys

February 2, 2011

Location: Hanover, NH
There’s something incongruous about a 20-pound bird sitting in a tree with branches barely fatter than twigs, but that’s exactly where I found this Eastern wild turkey (Meleagris gallopavo silvestris). She was obviously after the red berries that covered this young ash. A dozen of her friends strutted on the ground under her, jauntily pecking at the red raindrops that fell every time she moved. About 90% of a wild turkey’s diet is plant matter. During the winter, they often feed on the fruit that hangs on the longest, not only ash berries, but also barberry, rose hips and apples.
It’s so nice to see wild turkeys in such abundance again! When I was a kid, they were as rare as the Northern Lights on an overcast night. In fact, they had totally disappeared from New Hampshire about 150 years ago due to loss of habitat and unregulated hunting. Today, about 25,000 wild turkeys forage for berries, bugs and seeds in the Granite State, thanks to a relocation effort that began in the 1970s.
Turkeys can run up to 20 miles per hour and fly twice that speed, yet the one in this picture was happy to munch on berries as she watched me with a wary eye, at least for a short while. She soon hopped down to the ground then followed her friends under a fence and into the woods. It was remarkable how so many large birds could instantly disappear. Interestingly, by spring, this flock will likely disperse as the hens, toms (mature males) and jakes (young males) don’t mix during the mating season. One dominant tom gets all the girls.

Kathy and the Woodpeckers

February 1, 2011

My wife Kathy’s passion for birds did not match my own – though I thought it did when we were courting.

Courting, as some of you may recall, was a quaint and elaborate pre-marital ritual of testing and pleasing your prospective partner to determine whether you were more than temporarily compatible or deluded. (It’s since been superceded by immediate co-habitation.)

When I was writing my PhD thesis, I signed up for a ten week, non-credit “course” in birdwatching to allow me one sane day per week. The course met at dawn on ten consecutive Spring Saturday mornings. Kathy showed up every Saturday at dawn.

I thought I had hooked up with a perfect mate: a beautiful, smart, sensible, sensitive woman. BONUS: she too loves birds. It turns out she was my ideal mate for near forty years; but she loved a certain birder (me) more than she loved the birds.

That’s not to say that she didn’t like birds. She did. But they had to be special: i.e., big, colorful, stationary, and close. The little flitty ones she didn’t have much patience for, no matter how rare, delicately beautiful or sonorous.

Birds were just one of many things she was interested in: her family, skydiving, camping, traveling, Star Wars paraphernalia, garage sales, gardening, photography, water-colors, wretched soap operas, lighthouses, hot air ballooning, animals of all kinds, a good mystery, the internet – and especially the frail, difficult, and rejected kids that she tended as a school psychologist. The list of enthusiasms is long.

When she saw Pileated Woodpeckers this past summer, she was delighted. Here was her perfect North American bird. Although I’d seen them often, even in our own yard, she had whiffed on them repeatedly for over forty years.

We were on a small, hilly island in the middle of Lake Temogami in northern Ontario. Our hosts suggested that there was a spectacular vista on the other side of the island. Although Kathy could barely walk and was in excruciating pain (from what we thought was sciatica but turned out to be bone cancer of her sacrum and femurs), she couldn’t resist an opportunity for a mini-adventure or the possibility of a good photograph.

Even in her pain, Kathy somehow got ahead of the rest of us. When we caught up at the top of the island, Kathy was beaming. She showed us what she’d just shot on her digital camera. “My new favorite bird!”

There was not just one but three spectacular Pileated Woodpeckers, just as she had wanted them: big, colorful, stationary and close. The photograph of them above is the last nature photograph she ever took.

Rest in peace, my “Lifer” Kathryn Manix Walz
October 16, 1945 — January 20, 2011

Something Big Lives Behind my Stove

January 31, 2011

There are few good reasons to pull a stove away from the wall in anyone’s house. Maybe there’s a portal to a secret dimension where you never grow older or there’s a treasure vault hidden by a bootlegger in decades past. I was simply looking for the stove model # and what I found was horrifying.

Typically the items discovered behind any large appliance include Chinese takeout menus, diamond-grade pasta noodles, the fridge magnet letters X or J and maybe a pet hamster that has long since been eulogized and buried. But what I saw sent me reeling. I wouldn’t even dare take, let alone post a picture. Cast about on the tile behind the stove was a ring of spider appendages that looked like a skeleton poking up through the sand in the desert. Each of the eight, L-shaped, stiff-haired legs measured nearly two inches. Absent were any other body parts. Something big ate this spider. Something big lives behind my stove.

Shouldn’t I be content that the hideous creature that entered my house uninvited has been unceremoniously dispatched? It’s bad enough knowing the spider was inside these walls but something captured, killed and devoured this beast.

Days later I noticed a conspicuous pile of scat on the floor. It looked like a tiny tootsie roll left in the sun to long. I cleaned it up. The next day there was another. I cleaned that too and like a kid waiting for financial compensation from a tooth fairy, I came out the next morning to see if something had been left behind again. And it had. Not particularly magical.

My dad was visiting that day and I asked if he knew what it was. “That’s skink poop” he said with absolute certainty. It should be noted that not only have I cleaned up his quote for this post, but he is also an expert on the matter.

Days later I spotted the brilliant turquoise tail of a juvenile Five-lined Skink (Plestiodon inexpectatus) zip under the fridge and suddenly it all made sense. I made a deal with the skink – you eat the spiders, I’ll clean up your poop.

Termite Surprise

January 28, 2011

One by one they left the branches and surrounded me. The fact that I was there was incidental. Termites were swarming……..and the blue- gray gnatcatchers were gobbling them up. The click, click, click sounds of snapping beaks surrounded me as I realized that a small mixed flock, pine warblers among them had joined in. I stood still and just witnessed the birds hovering and snapping around and through the swarm. If I wanted to and my reflexes were fast enough I’m sure I could of nabbed a bird or two. But I just wanted to soak it up. At first the insects were hard to see but the filtered light coming down through the branches highlighted the tiny wings and made it easy for me to catch. For the termites that thought they had escaped the beaks of those small birds destiny called. They were soon gobbled up by the army of swallows just above, another resource partitioning event right before my eyes.
How did I luck out to witness such a food fest? These small song birds normally glean their prey off branches and buds, keeping themselves camouflaged from larger predators. The swarm was coming from the saw palmettos that were under scrub oaks edged by wax myrtle, rusty lyonia and beauty berry shrubs. They left the comfort of the leaf cover to grab their prey and then fly back to their perch. I was walking on a path that ran right through the saw palmettos so, essentially, I was in the right place at the right time. I walk that path often, so the birds may have been used to my presence. Or, they may just have been hungry enough to navigate around me. I think this is a key to any good nature observation. Know your local seasons and the ebb and flow of the food web. I pay attention to the larvae in the shrubs and trees as well as the mosquitoes and deer flies that emerge when it gets a little drier and hotter. But I had forgotten about the termites…bonus!

Carp: Worth Carping About?

January 27, 2011

We walk along the water’s edge at a lake near Boulder, Colorado. With each laborious step, my boot presses into a slick sheen of monochrome muck. As I lift my foot for the next stride, a glistening glob of gray goop clings to the sole. It smells of sewage.

Just ahead, my companion has spotted a pod of fish. Trout can’t survive in the murky, heated water of this urban reservoir, but it’s ideal habitat for carp. In fact, they’re at least partially responsible for its muddy character. Carp feed by rooting around on the bottom. The action of their snouts and the wallowing of their bodies stir up dirt and debris, clouding the water and covering rocks and plants. Silt stirred by carp can smother the eggs of other fish and contaminate habitat for a host of aquatic insects.

Transported to the United States in the mid 19th century, carp are native to Asia. They grow quickly and tolerate high water temperatures. Female carp in their prime may produce as many as two million eggs. It’s little wonder they often crowd out native minnows and other species of fish. Considered a delicacy in parts of Europe, carp were released in American waters in hopes they would become a commercially valuable resource. But few people like to eat them.

My guide has hooked a carp with his fly. The brute runs toward the middle of the lake, its stout, strong body bending his rod in a severe arc. He smiles widely. Though a master hunter of trout, he’s a carp dude, one of a small cadre of anglers who, despite their academic disdain for this interloping transplant, relish the challenge of fooling a crafty carp with a fly and bringing its bulk to hand.

Like many non-native species with a deleterious impact on native life, carp are here to stay. The decision to scatter them, willy-nilly across North America waters, can’t be undone. They can be managed, but not eradicated, cussed but not conquered. Carp all you want, but we’re stuck with carp.