Earth Almanac: July/September 2002
Audubon July/Sept. 2002
At twilight a black funnel cloud forms in a windless and otherwise unblemished sky. But instead of sucking up the building over which it hovers, the building sucks it down until only a few wisps, swirling like candle soot, fade into the gathering darkness. Swifts, massing for fall migration, have dropped into their night roost in an unused chimney. In the Northwest the species is Vaux's swift; east of the Rockies it's the chimney swift. Both are often the victims of chimney sweeps or of fires kindled by people who don't know the birds are there. Swifts, related to hummingbirds, have cigar-shaped bodies; long, narrow wings; and feet so puny they can only cling to vertical surfaces. Wings quivering, large mouths agape, they orbit parks, fields, and backyards, describing wild loops, chipping loudly. During the day they live in the air, eating, bathing, copulating, gathering nesting materials, and possibly sleeping on the wing. If you have swifts roosting or nesting in your chimney, close the damper to keep the birds from falling into the fireplace. Despite the oft-told wives' tale, nests pose no fire hazard, and removing them is a violation of the Migratory Bird Treaty Act. If you don't have a chimney and want swifts, you can set up a swift tower. For plans, log on to www.tpwd.state.tx.us/nature/birding/chimneyswift.
Photo by Buddy Mays/Corbis
Meet Your Skinks
Now, when they are seeking winter dens in logs, mammal burrows, woodpiles, and stonewalls, is the best time to meet neighbors you may not have known you had. If you live east of the Great Plains and outside northern New England, your state probably hosts five-lined skinks. Some five-lined skinks indeed have five lines—from neck to mid-tail. But others, particularly older ones, do not. The head of the adult male is redder than the female's. When a male sees another five-lined skink, he charges with his mouth wide open; if the stranger turns out to be a rival male, a fight ensues. Juveniles have bright-blue tails, presumably to decoy natural enemies away from vital body parts. When a predator or person grabs the tail, it detaches, then wiggles seductively. Sphincter muscles in the stump close off the caudal artery, thereby preventing excessive blood loss. The lizard then grows a new tail, but one with different scales and more subdued coloration.
Fragrance of Indian Summer
There is a pause between summer and fall, when nights are cool and full of cricket song, when swamp maples blush, and when limbs along the meadow's edge bend low with fruit. Among the first of these fruits to ripen are wild grapes—about 30 species throughout our nation, mostly native and often natural hybrids. Wild grapes feed a host of wildlife, including bears, foxes, skunks, opossums, doves, grouse, quail, wild turkeys, prairie chickens, woodland thrushes, woodpeckers, cardinals, and at least 100 other songbirds. The fragrance of wild grapes carries so far and is so unmistakable that the best way to find them is with your nose. There are plenty for everybody, so don't hesitate to pick some; their tartness makes them perfect for jelly.
Illustration by James Prosek
Little tunny, a.k.a. false albacore and fat Alberts, patrol tropical and subtropical waters on both sides of the Atlantic. But when ocean temperatures peak in late summer, they stream north as far as Maine and Great Britain in shimmering, elliptical shoals that can cover two miles on the long axis. Most people, even experienced anglers, think they're bluefish or striped bass. Watch for the sickle tails and geysers of spray as these mini tunas swill anchovies and other baitfish. Often the school is attended by a cloud of screaming terns and gulls that dip and dive for leftovers. Few of these short-lived, fast-growing fish weigh more than 15 pounds, but when they take your fly, they'll have 50 yards of line off the reel before you can snatch your bruised knuckles from the spinning handle.
One morning in early fall, your lawn may be draped with a silver fabric bright enough to mimic a pond's surface but so fine it seems to have no mass. Chaucer called the phenomenon one of the unsolved mysteries of the universe. Subsequent investigators attributed it to evaporated dew. It took a pig to pin it down: "The baby spiders felt the warm updraft. One spider climbed to the top of the fence. Then it did something that came as a great surprise to Wilbur. The spider stood on its head, pointed its spinnerets in the air, and let loose a cloud of fine silk. The silk formed a balloon. As Wilbur watched, the spider let go of the fence and rose into the air." That passage, from E. B. White's Charlotte's Web, remains one of the best descriptions of how many juvenile North American spiders disperse. Darwin observed silk-riding spiderlings when the Beagle was 60 miles from land. In May 1884, 10 months after the most powerful volcanic explosion in recorded history sterilized the island of Krakatoa, the first scientist to set foot on the site found only one life-form: a spiderling. Census traps mounted on airplanes have caught spiderlings at 15,000 feet. Occasionally, they'll ascend to the jet stream and cross the Atlantic.
Bully for Bullwinkle
From the Rockies east, moose, earth's largest deer, are filtering south as the species gradually rebounds from the unregulated hunting of the 19th century. In New England, moose are even colonizing suburbia; recently they've been encountered in southern Connecticut. If you have seen heart-shaped tracks too big to be white-tailed deer, listen for the vocalizations of rutting bulls—moans, whines, and a series of grunts that, while not loud, are so deep that they carry long distances. Moose, which are at the southern fringe of their range in the contiguous United States and therefore don't need the thermal cover that deer require, are benefiting from clear-cutting. The practice encourages nutritious leafy growth and, at least in the north woods, it destroys deer habitat. This, too, is beneficial for moose, because deer are commonly infested with a brainworm, which they carry with apparent impunity. But when the same brainworm infests moose, it blinds, maddens, and eventually kills them. There are now so many moose in Maine, Vermont, and New Hampshire that these states have reinstated hunting seasons. In Maine, 85 percent of the hunters who drew permits in the 2001 "moose lottery" killed a moose. Despite the moose-hunting tip offered by waggish critics—"Take 10 steps back and shoot"—the resource is being superbly managed.
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