The changing natural world at our doorsteps | By Patterson Clark
March 22, 2011
Red maples set fruit
Some red maples sport both male and female flowers -- but on separate branches.
These female blossoms are already developing winged fruits, which will ripen before the leaves have fully expanded.
March 29, 2011
Spicebush: A blooming panacea
In March, the early-blooming, sweet-smelling flowers of spicebush enliven local parks with a greenish-yellow tinge.
Twigs bear clumps of either male or female flowers. Each bloom is only about a quarter-inch in diameter.
Emerging leaves are fragrant with camphor, as are the twigs. Both can be steeped to produce an herbal tea.
The Cherokee drank the tea as a tonic, a cold remedy and for blood and menstrual problems. The Iroquois used "fever bush" to lower fevers. Mohegan children chewed the twigs to rid themselves of worms.
During the Civil War, some Confederate soldiers drank spicebush tea, which tastes very much like a spicy, aromatic black tea.
A 2008 study revealed that spicebush bark extract strongly inhibits growth of both Candida albicans yeast and the fungus that causes athlete's foot.
The shrub can also be a balm for the garden: Deer avoid it, so the bush thrives in both woodlands and on urban lawns.
April 5, 2011
House wrens: Success in the city
House wrens will soon arrive from as far away as Central America. As they fill the spring air with effervescent song, they'll also be aggressively pursuing suitable nesting cavities, sometimes destroying the eggs and nests of other small birds.
As they hunt for food and collect nesting material, house wrens find spider egg sacs, which they add to the nest. When spiders hatch, they devour mites and other nest parasites.
House for wrent
If you like tiny, chatty neighbors, you can build a home that will attract them. A single plank of lumber, 1" x 6" x 48", can be cut and assembled into a house-wren home. The box should be mounted to a wall or post six to 10 feet off the ground.
The benefits and perils of suburban nesting
A house wren born in a city nest box stands
a better chance of fledging (flying the nest) than do catbirds, mockingbirds, robins and cardinals, which build open-cup nests. A wren's cavity nest, with its small entrance, provides more protection from crows and
jays, the primary nest predators of the Washington area.
Suburban bird nests tend to be less bothered by predators than are rural nests, which fall prey more often to small rodents. But while suburban wren babies are more likely to
fledge than rural wrens, they develop more slowly and are less robust, perhaps because their insect food is of poorer quality.
For a suburban mother wren, more time spent searching for food means less time brooding (warming) her chicks, causing them to use up more of their energy to stay warm while she's away.
And once they leave the nest, smaller, weaker suburban wrens are likely to face an environment more challenging than in the country: more pollution, more noise, more cats.
SOURCES: Cornell Laboratory of Ornithology; "Reproductive Success of House Wrens in Suburban and Rural Landscapes," The Wilson Journal of Ornithology; "Quantifying avian nest survival along an urbanization gradient using citizen- and scientist-generated data," Ecological Applications; Plans redrawn from "Woodcrafting for Wildlife," by Jerry Hassinger
April 12, 2011
The surprising sex life of leopard slugs
Gardeners raking away the last tired leaves of winter will often expose clusters of glistening slug eggs, which were laid late last fall. As the weather warms, each tapioca-pearl-sized egg can hatch into a minuscule slug.
For some baby slugs, mom and dad are the same individual: Slugs are hermaphrodites, capable of fertilizing themselves.
But most often, slugs mate with another slug. On warm nights, the common leopard slug, a native of Europe, engages in an elaborate courtship ritual. Two slugs climb to a high spot, where they twist tightly together and lower themselves onto a thread of mucus. While suspended, they twine together their translucent male organs, which emerge from the sides of their heads.
After exchanging sperm, the slugs retract their organs or chew them off if they can't get them untangled. One slug drops to the ground and the other climbs back up the mucus cord, eating it as it goes.
Both fertilized slugs will lay hundreds of eggs, which also emerge from the sides of their heads. This garden caviar is often consumed by beetles, earwigs, shrews and birds, especially chickens, which will quickly rid a property of slugs and slug eggs.
The fortunate slug that hatches will need to survive for at least two years before it's mature enough to mate.
Since thay have little or no shell, slugs secrete much more protective mucus than do snails, but some people see them as unpackaged escargots. However, several factors may give pause to the potential slug chef:
Slugs should never be handled with bare hands, let alone eaten raw. From contact with rat feces, slugs may carry a parasite that can cause a potentially fatal brain disease in humans. Thoroughly cooking a slug or a snail should destroy any dangerous parasites.
Slugs are more likely to eat toxic fungi than are snails. Slug harvesters are advised to purge the poison from captive slugs by feeding them grain meal and lettuce for many days before cooking.
Soaking slugs in a vinegar/water solution will kill them and remove much of their mucus, but the cooking water must be changed a couple of times to get rid of all of the slime. The foul-tasting digestive gland in the slug's tail should be removed after cooking.
April 19, 2011
Dandelions: Eat your weeds
People who curse the dandelions dotting their manicured lawns this spring may not recognize a friend when they stomp on one.>
A dandelion's tap root can penetrate and loosen hard-packed soil, pulling up nutrients from as deep as 15 feet, making essential minerals available to other lawn plants, including turf.
Brought to North America by European colonists, dent-de-lion (French for "lion's tooth," named for its fang-shaped leaf margins) has been harvested for use as food and medicine for thousands of years.
Less bitter if picked before the flowers appear, leaves are rich in iron, calcium, zinc, potassium and vitamins A, B complex, C and D. Used medicinally as an appetite stimulant and to support kidney function, leaves are a nutritive medicine, acting as a diuretic without depleting the body of potassium.
Torn apart and eaten raw in salads, the bittersweet yellow flowers contain antioxidants. They can also be fermented into dandelion wine.
Roots are boiled or sauteed for eating, or roasted to make a coffee substitute. Dandelion root may improve gastro- intestinal, liver and gallbladder function, but shouldn't be used with an irritable stomach or bowel.
Dandelion root may even help fight cancer. In a recent study on skin cancer cells grown in the laboratory, scientists from the University of Windsor in Canada demonstrated that an extract from the root causes malignant melanoma cells to die without damaging healthy cells. Authors of the study suggest that the effect is produced not by a single chemical agent but by the combined effects of numerous compounds found in the root.
Making melanoma self-destruct
In vitro human melanoma cells suffered apoptosis, or programmed cell death, after exposure to dandelion root extract.
SOURCES: University of Maryland Medical Center; Steve Brill; Maine Organic Farmers and Gardeners Association; "The Efficacy of Dandelion Root Extract in Inducing Apoptosis in Drug-Resistant Human Melanoma Cells," Evidence-Based Complementary and Alternative Medicine
April 26, 2011
| An exotic disease is wiping out flowering dogwoods in the Appalachians.
As dogwood blooming peaks in late April, rusty-red splotches may appear on some flowering dogwood blossoms. These aren't the allegorical crucifixion-nail stains always seen at the tips of the flower bracts, but rather something truly diabolical: dogwood anthracnose, an exotic invasive fungus that is rapidly annihilating native dogwood trees.
Since it was first noticed in New York the late 1970s, Discula destructiva may have already wiped out more than half of the native
dogwoods in the Appalachians. Central Maryland has lost almost 75 percent of its dogwoods; 80 percent of Northern Virginia mountain dogwoods are gone. In some areas the tree has vanished.
Forest health may decline if deprived of the dogwood's contributions. The tree pulls calcium from the soil, concentrating it in its leaves. When leaves drop and decay, the mineral becomes available to other organisms and helps prevent acidification of soils. Many birds and mammals depend on
dogwood fruit as a food source in the autumn.
Dogwoods tend to be more resistant to anthracnose if they grow in higher-temperature, low-humidity areas with plenty of sunlight and adequate soil moisture. Regular controlled burning of forest floors helps maintain some of those conditions, and may be the most effective way to ensure the survival of this beloved native tree.
SOURCES: Cornell University, North Carolina State University, International Journal of Forestry Research, Forest Ecology and Management, forestencyclopedia.net
May 3, 2011
Drain flies: Denizens of the sink
The dead skin, spit, hair, food and any other waste that you send down the drain are gifts from above for the humble drain fly.
In spring the fly emerges from drains and sewers to mate and lay eggs, which in less than two days hatch into tiny maggots that feed on the gelatinous scum lining drains and sewers.
After two weeks of feasting, the maggots develop a hard shell in which they will pupate and from which they will emerge in a day or two as small furry adults, also known as moth flies.
While they may appear sedentary, quietly hanging out in the tub, the adults can react quickly, flying away from any attempt to swat them. They stay alive by drinking waste water or flower nectar, if they can find it.
Homeowners can curb the drain-fly life cycle by cleaning their pipes with boiling water and a stiff wire brush. Another alternative: natural drain cleaners containing bacteria and enzymes you can Google them that consume the scum before the maggot gets its chance.
May 10, 2011
Bright buildings are hazardous to migrating birds
At 5:30 a.m., Anne Lewis and Elizabeth Shope begin searching the plazas that front about a dozen buildings at the eastern end of downtown Washington.
They are are looking for dead or injured migratory birds, casualties of modern architecture.
Lewis, an architect, is conducting a survey of fallen birds for Lights Out D.C., a project of City Wildlife, a nonprofit organization that she heads. Like similar groups in other urban areas, City Wildlife wants building operators to turn off their lights at night.
Lewis first stops at the Thurgood Marshall Federal Judiciary Building, which has several attributes that can put a bird on a collision course: The front of the building has converging planes that "funnel birds into the glass at the entrance," Lewis says. Massive foliage inside the building can attract a bird looking for a safe place to perch. "The three major problems here are transparency, reflectiveness and light," she says.
Since night-migrating birds use light signals (stars) to help them navigate, migrants become confused by, and even drawn toward, brightly lit buildings. "Look," Lewis says, pointing at the building, "every single light is on."
Of course, it's not the light that kills them. It's the glass.
Birds have problems detecting glass, which can be either too transparent, inviting them to fly through it, or too reflective, presenting birds with a deadly illusion of trees and sky.
Many birds are killed instantly by the impact, but some survive. Lewis recently rescued a stunned ovenbird, which she held in a protective cage until it regained its senses. She released it into woodland habitat near a water source. Less fortunate was a whippoorwill that perished after attempting to fly through the Hart Senate Office Building.
On L Street, beneath the mirrored skywalk of the D.C. Convention Center, traffic has squashed a gray catbird into a pancake of charcoal feathers. A flattened sparrow lies nearby. If the birds had fallen onto the sidewalk instead of the street, early-morning maintenance workers would probably have disposed of them.
That's one reason why Lewis, Shope and eight other volunteers get an early start. But, Lewis adds, "we also have to get there before the crows do." At dawn, crows run their own surveys, snatching up collision victims for breakfast.
SOURCES: USDA Forest Service; Jim Monsma, www.citywildlife.org
The clear glass facade of the Thurgood Marshall Federal Judiciary Building is the site
of numerous bird impacts.
To reduce collisions, architects can choose to use glass covered with patterned or ultraviolet reflective coatings. (Birds can see UV light but humans can't, so the pattern
is almost invisible to humans.)
Turning lights off at night would greatly reduce bird deaths.
May 17, 2011
This plant growing alongside the C&O Canal resembles a grass, but is more closely related to irises.
May 24, 2011
For most of the year, the male broad-headed skink is olive-brown, a color that helps him blend into his favorite habitat of moist oak forests.
But during breeding season in the spring, high testosterone levels trigger a flush of color to his head, which in May resembles the end of a red-hot poker.
Not surprisingly, the males with the biggest, reddest heads tend to be the ones that get to mate with the largest females, which lay the most eggs.
When challenged by another male, the skink will try to intimidate his opponent by displaying the size of his head. If that swagger doesn't work, a fight will ensue, with the loser banished to the margins of boss skink's territory. There, young and defeated males lurk, waiting for a chance to sneak some time with the closely guarded receptive female.
In the summer, females lay clutches of eggs in rotten hardwood logs, where they carefully monitor and protect them.
When they hatch in August, young skinks wear their mother's black and tan stripes, but sport bright blue, quick-release tails.
A predator grabbing a skink's blue tail will probably lose the rest of the lizard, which can scurry away and can grow another tail.
Sources: Savannah River Ecology Laboratory, Copeia, Journal of Herpetology, Herpetologica
May 31, 2011
Narrowleaf plantain: Produce from pavement
Of the plants able to thrive in a sun-baked sidewalk crack, few are more successful than a perennial herb that arrived with early European colonists.
In the spring, narrowleaf plantain, or ribwort, sends up a long, thin stalk topped with a small pineapple-shaped flower head. A ring of tiny white anthers, which appear to orbit the head, release a pollen that can trigger allergies this time of year.
The plant can mitigate its weedy, sneezy nature, however, by offering some oft-forgotten qualities:
The crushed leaves produce an astringent, antibacterial and anti-inflammatory juice that some people apply to cuts, insect bites and stings. A bruised leaf smeared onto a mosquito bite will stop the itch.
Leaves can be eaten like other dark greens, once they're stir-fried or boiled. Young leaves are preferred, but older leaves can be used after their tough, parallel veins are removed. The leaves are chockablock with antioxidants, rivaling those found in blueberries.
Anyone harvesting plantain for its benefits should seek out plants growing in sunny, pesticide-free lawns. And avoid the sidewalk plants, which sometimes get a squirt from neighborhood dogs.
Sources: Journal of Food Science; Allergy; Australian Naturopathic Network
June 7, 2011
Earlywood's over, latewood begins
As summer approaches, pin oaks stop producing spring wood, the layer now just under the bark. These earlywood vessels began developing well before the tree's leaves were fully formed. Their cells were fed not by sugars from this year's leaves but by starches stored in the wood produced last summer, so-called latewood.
"The condition of earlywood is more of a function of last year's growing season than this spring's climate," says National Forest Service plant physiologist Kevin T. Smith. Sugars produced by the leaves that are out now will be used to build this season's latewood vessels, which are smaller and structurally stronger than earlywood. A complicated combination of hormonal, genetic and moisture factors triggers the growth of latewood vessels, says Smith.
When hot weather arrives, leaves become inefficient at making sugars, and oak trees curtail production of wood tissue.
"They have about an eight-week window when they grow the bulk of their annual wood," says Richard C. Murray, author and principal arborist at Shannon Tree and Landscaping in Silver Spring. "When temperatures soar into the 90s, the growing process slows dramatically."
At this point, trees begin to alter the contents of their woody cell walls, forming a cementlike structural component called lignin. They also begin to convert sugars to starch for storage.
Cold weather and short days will halt the green growing season, but trees are never fully dormant. In the fall and winter they grow non-woody roots and regulate stored starches for cell metabolism. "Trees are on 24/7," says Murray. "They are always up to something."
As an arborist, Richard
C. Murray has spent a lifetime slicing through wood, but he seems less interested in chain saws than in what they can reveal about the nature of trees.
In his recently revised "Tree Biology Notebook," Murray provides detailed descriptions of the structure and growth of wood and its reaction to damage, stress and pathogens.
Pictured here are a couple of examples collected by Murray:
Whorled branch cores look like spokes inside the trunk of a white pine, top. The cores were resistant to the rot that consumed the center of the tree, which walled off the damage and continued to grow new wood for more than 20 years.
When this 65-year-old hickory wood, bottom, was 28 years old, a sapsucker chipped out a series of holes in the bark, seen here as a dark brown ring. The bird returned to feed on sap and insects drawn to the wounds.
Photos from Richard C. Murray
June 14, 2011
Firefly falls for femme fatale
During a June dusk, common eastern fireflies (Photinus) emerge from their daytime hiding places in the grass. Males climb out to the tips of vegetation, take flight and begin blinking their greenish yellow lanterns for a third of a second every 5 1/2 seconds. Females stay grounded but observe the performances, waiting two seconds after spotting a male's flash before blinking their own lanterns, signaling a receptiveness to mating.
But some males responding to a come-hither beacon may find themselves face to face with a deadly seductress. Pennsylvania firefly (Photuris) females can imitate the receptive flash of their Photinus cousins, drawing in males of that species, which they will try to kill and eat.
But lady Photuris is after more than just a meal. Her species lacks a compound that Photinus has in its blood. After feeding on a Photinus male, a Photuris female will be endowed with her victim's chemical repellents, which will prevent her from being devoured by spiders and birds.