The changing natural world at our doorsteps | By Patterson Clark
November 3, 2009
Fall fruits for birds
Pokeweed fruits, left, are ripe and ready for birds to devour. (Beware: The seeds are poisonous to people.) In a few weeks, the first hard freeze will collapse the plant, but underground stems will endure, sending up fresh "poke salad" leaves in the spring (also poisonous unless cooked twice in separate water).
Birds are also eating the tangy hips of multiflora rose , right. In the 1930s, the Soil Conservation Service encouraged farmers to use the rose as a "living fence," which would control erosion and provide food and cover for wildlife. The rose, a native of East Asia, quickly became an invasive plant. And birds continue to spread it as the seeds pass through their digestive systems.
SOURCES: National Park Service; University of Maryland Medical Center
November 10, 2009
Falling leaves create an autumn air show
Every leaf performs a unique dance from twig to ground, an aerobatic display consisting of one or more of the following:
November 17, 2009
Starlings generate upticks
in Web searches
At sunset, Washington commuters can often look up to see a surprising swarm: huge flocks of starlings, swirling over office buildings and into trees. Apparently, many of these commuters go online when they get home and investigate. The Googling public's interest in European starlings seems to peak when the birds are breeding in the spring and flocking in the autumn. This fall's record of searches reveals a sharp spike in human interest.*
Introduced from Europe in 1890, starlings have advanced across North America, out-competing native birds for nest cavities and causing $800 million a year in agricultural damage. Studies by the USDA indicate that starlings are capable of spreading a host of diseases to livestock and humans.
SOURCES: Google Insights for Search; USDA; Keith L. Pardieck, Patuxent Wildlife Research Center; British Trust for Ornithology
November 24, 2009
Crickets come in from the cold
A cricket at the hearth may be a traditional sign of good luck, but it's also a sign of winter approaching. Cooler weather can drive the insect indoors, seeking a warmer environment for the final weeks of its life. A distant cousin to cockroaches (a traditional sign of filth), field crickets are slower-moving and uninterested in your garbage, preferring dark, damp spots where males sing by rubbing their wings together for as long as eight hours a day.
Scores of cricket species are found in the U.S., each with a unique song. Explore cricket songs at the University of Florida.
SOURCE: University of Florida Department of Entomology
December 1, 2009
Acorns employ varied germination strategies
White oak acorns aren't waiting for spring. The lucky ones that landed on soft soil -- and were missed by squirrels -- have had a warm, wet season to germinate and sink their radicles into the earth. Freezing temperatures will pause the rooting, but spring warmth will resume the growth and coax out leafy shoots. After a year, a tap root can stretch as much as a foot underground.
Pin oak acorns are a study in patience. They develop on the twig for two growing seasons before dropping and require a winter's cold treatment to germinate. A thick, waxy coating allows the little acorns to stand for six months in cold water without suffering damage.
The white oak group of oaks have smooth, rounded leaf lobes. Acorns mature in six months; some are sweet and edible. Wood is generally whiter than red oak. Species include white oak, overcup oak and bur oak.
The red oak group of oaks sports leaves with bristle-tipped lobes. Acorns are very bitter; wood is generally redder than white oak. Species include pin oak, northern red oak and scarlet oak.
SOURCES: U.S. Forest Service; Illinois State Museum
December 8, 2009
The annual Geminid meteor shower occurs during a dark, new moon this year, offering a display of as many as 80 shooting stars an hour -- unless a curtain of clouds blocks the show. The shower is caused when the Earth passes through the dust cloud that trails a 3.2-mile-wide asteroid named 3200 Phaethon. Light streaks mark particle paths as they burn through the atmosphere at 22.5 miles per second.
Even in the District of Columbia, where light pollution blocks all but about 80 stars, some of the brighter meteors should be visible. At midnight Sunday or Monday, an observer lying down (in a sleeping bag) with her head to the north and feet to the south, will have a view similar to the diagram above. The trails of Geminids will appear to radiate from a spot, or radiant, near the star Castor in the constellation Gemini.
SOURCES: JPL, NASA; University Corporation for Atmospheric Research; International Meteor Organization; meteorshowersonline.com; transientsky.wordpress.com
Flea infestation rates peak in February at about 68 percent, soon after squirrel babies are born. The insects jump on and off the mammal, so a cozy squirrel's nest may harbor a horde of fleas.
December 15, 2009
Gray squirrels are hosts
to irritating ectoparasites
"When you see a squirrel scratching, it's probably going after fleas," which tend to roam all over the animal, says Lance Durden, a Georgia Southern University entomologist who studies rodent ectoparasites. "But lice probably itch, too," he adds.
While cold weather suspends the activities of biting flies and mosquitoes, the flightless insect pests that torment wild mammals, including gray squirrels, are just beginning to enter their peak season.
Squirrel lice are most abundant in the winter, with infestation rates at about 100 percent. Why that rate drops to about 50 percent in July and August is unknown, but Durden thinks it may have something to do with hot weather and a squirrel's summer coat.
Durden once counted about 300 lice on one squirrel. The blood-sucking insects are concentrated mostly on a squirrel's head, shoulders and back of its neck — rarely on the belly, where the rodent can get at them with its teeth. Baby lice (nymphs) congregate on a squirrel's rump, where there is probably less competition from adult lice.
On the squirrel, female lice outnumber males, presumably because "females stay down close to their food source," says Durden. "Male lice are more vulnerable since they engage in risky behavior," clambering across the squirrel's fur to get at the females.
Durden assures us that "lice are quite host-specific, so there is no chance of squirrel lice infesting and feeding on humans."
Many flea species are a lot less picky about their meals. Bird fleas often feed on squirrels; and squirrel fleas feed on birds — and have been known to bite people, too.
From Vince Smith
An adult female Neohaematopinus sciuri, above, is a 2-millimeter-long sucking louse, one of three louse species found on gray squirrels.