| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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Naturalist's Almanac What to look for this Summer July Even as June comes to a close and local birds are still nesting or tending their young, a dozen or more shorebird species from northern climes have already completed their breeding season and are sweeping down through California. The change is subtle: at first a few sandpipers show up in the shimmering heat waves of the state’s sun-baked mudflats, then numbers build to flocks of hundreds or thousands. On a local scale these seem like scattered occurrences, but the birds pop up all over California shorelines simultaneously. Mudflats around San Francisco Bay and along the coast near Point Reyes are some of the best in the state for viewing migrating sanderlings, western sandpipers, least sandpipers, dowitchers, and numerous other shorebirds. Prior to the opening of Tioga Pass Road in 1915, the Sierra sulphur butterfly was considered an extreme rarity known only from a few largely inaccessible sites in the High Sierra. Highly prized by museums and collectors around the world, most specimens of this small greenish butterfly had to be purchased from an entrepreneurial homesteader named John Batiste Lembert (of Yosemite’s Lembert Dome fame) who carefully guarded the secret of his source. The road opening revealed Tuolumne Meadows and other subalpine meadows around Tioga Pass as the home range of this butterfly. Here, among the dwarf bilberry plants that provide larval food, the Sierra sulphur is a surprisingly common and easily found butterfly from mid-July to mid-August. How it came to be isolated in such a tiny patch of the High Sierra, far from any close relatives, is one of many riddles left to us by the Ice Age. Almost single-handedly, the simple acorn powers entire ecosystems over vast areas. Formed of cotyledons, or seed leaves, held within a protective seed wall, an acorn begins life as a tiny nubbin in early summer and swells to full size by the end of the season before turning brown and signaling its ripeness to seed collectors. A rich combination of carbohydrates, fats, and proteins, acorns are consumed by a list of organisms that would fill several journal pages. Acorn woodpeckers, woodrats, western gray squirrels, and Steller’s jays are among the many who feverishly gather and hide these treasured seeds for later consumption, dispersing them across the landscape in the process. Overlooked seeds have a ready storehouse of energy to sustain them for a period of rapid growth, something that makes a huge difference in the variably shaded world of oak woodlands, where competition for sunlight and space can be fierce. Try spotting incipient acorns in July, long before they take on their familiar shape. August Cryptically camouflaged to match the bare ground they frequent, band-winged grasshoppers create a sudden flash of bright color from their otherwise hidden hindwings when they leap into flight. Unlike other orthopterans such as crickets, band-winged grasshoppers stridulate, or sing, by snapping their wings in flight. Hardly a song, these calls sound like an electric buzzing or a crackling that can be easily mistaken for a rattlesnake. Familiar to anyone who visits the High Sierra in late summer are Sierran blue-winged grasshoppers, a type of band-winged grasshopper that pops up all over dry hillsides like electrified popcorn as hikers pass by. Males hover over these hillsides issuing their odd crackling sounds in hopes of being noticed by females resting on the ground below. Easily accessible locations to view these displays in the Sierra Nevada are slopes along the Pacific Crest Trail just south of Donner Pass. While true frogs (family Ranidae) are usually found in lakes, ponds, and marshes where waters are sluggish and warm, one notable exception is the foothill yellow-legged frog, which lives solely in the streams and rivers of the Pacific slope. Along with this lifestyle shift comes the need to curtail egg-laying until after stream flows diminish in late spring or early summer. Even a single late rain can wash away egg masses or coat eggs in silt, so yellow-legged frogs bide their time. As a result, this is one of the rare instances where you can expect to find tadpoles as late as August. The tadpoles are grayish with flecking like gold dust among the cobbles. Look for them in quiet shoreline areas of streams and rivers in the Coast Ranges south to Los Angeles, and the length of the Sierra Nevada’s west slope below about 6,000 feet.
September is the beginning of conifer cone season, although this natural event can be overlooked because most activity takes place more than a hundred feet up in trees. One’s first hint may come by finding a profusion of winged ponderosa pine seeds covering the ground. Cones on all the trees around will be fully open, spilling seeds like dusty snowflakes whenever a wind whirls by. At the same time, red firs and white firs high in the mountains can become so laden with ripe cones that treetops look burnt orange from a distance. Meanwhile, chipmunks, squirrels, and jays work in a frenzy to collect the seeds before they are all gone. One of the most significant turkey vulture migrations north of Mexico was discovered less than ten years ago in the Kern River Valley east of Bakersfield. Observers now regularly document close to 30,000 vultures each season, with daily counts reaching as high as 4,500. For those who think vultures are unappealing, consider the words of Turkey Vulture Society President Bill Kohlmoos. Turkey vultures, he says, are “the most graceful soaring bird in the world,” playing with fine updrafts “much as a pianist plays classical music on a Steinway.” Curious viewers can check out the Kern Valley Vulture Festival September 27-30 (www.valleywild.org/tvfest.htm) or sign on to be a volunteer vulture observer by emailing vulturewatcher@yahoo.com.
David Lukas leads natural history tours and programs in the Bay Area. He can be reached at davidlukas@earthlink.net |