| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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naturalist's Almanac What To See This Fall October
By now the great conifer cone harvest is in the bag. Because conifer seeds contain upwards of 40 percent fat and of 50 percent carbohydrates and store well through the winter, they are an ideal food source for many types of birds and small mammals and are harvested with great enthusiasm starting in late summer. Birds such as jays tend to gather seeds released by mature cones. Squirrels, on the other hand, prefer to snip imature cones from the tree. They chew through the bases of cones, leaving twig tips, scales, and pieces of bracts littering the forest floor. Once on the ground, the hundreds of harvested cones can be collected and stored. Each cone may hold up to 200 seeds, but many have far fewer due to insect damage, other harvesters, or incomplete fertilization. To ensure they cache only the best cones, squirrels test each cone by chewing off sample scales, much like humans shucking corn ears at the store. At times, a squirrel may sit on a favored perch and completely empty a cone of its seeds, leaving only its central core and a pile of frayed scales and bracts.
In the narrow window between leaf drop and winter storms, bird nests can be spotted with relative ease. They invite close inspection—every nest is a marvel of design and material selection. There are the long, pendulous nests of bushtits hanging like gray socks amid oak boughs; the precise mud-and-stick nests of American robins, the silken thimbles of hummingbird mothers—and that's just for starters. Yet all share the same basic structure: coarse outer materials woven together with fine fibers and grasses, then lined with downy softness. The cuplike nest of the diminutive golden-crowned kinglet, for instance, is lined with around 2,500 feathers, while Anna's hummingbird cushions her eggs with countless strands of spider silk. The outer portions of some nests are camouflaged with bits of lichen and moss to help conceal their presence. Yet even after thousands of gathering trips and weeks of construction work, most birds rarely reuse their nests. The risk of parasite infestations in old nests helps keep many birds building anew.
Across California a tremendous dusting of cattail seeds announces the approach of winter. Sailing like white clouds from every marsh, millions of these microscopic seeds burst vigorously from eight-inch-long flower spikes and hitch rides on the first strong winds of autumn. So light that even faint gusts catapult them into the heavens, these seeds easily travel hundreds of miles before touching down again. Seeds lucky enough to land on shallow water immediately bail out of their traveling capsules (pericarps) and sink into the muck. After waiting through winter, a seedling sends out long roots. It may grow to cover half an acre with dense thickets of stems before it begins producing its own flowering spikes several years later. With each plant generating hundreds of spikes, and each spike containing 250,000 seeds, the cattail is one of nature's most prolific and successful plants.
Though no larger than a quarter-inch piece of string, Mono Lake brine shrimp exert a tremendous influence on one of California's most unusual lakes. Three times saltier and 80 times more alkaline than the ocean, Mono Lake is home to seven trillion shrimp found nowhere else in the world. All summer, these semitransparent relatives of lobsters and sow bugs keep the lake free of algae. They swim around mating and sweeping microscopic particles into their mouths with their long, frilly legs. But when lake waters cool in October, adult shrimp cast countless eggs into the lake's depths, then die. In their absence, algae proliferate so dramatically that the clear blue waters turn the murky color of pea soup through winter. Live brine shrimp are the main course for two million or so eared grebes that visit the lake during their migration south. November
November is an ideal month to experience the great pulsing torrent of the Pacific Flyway. Each autumn, this virtual river funnels migrating ducks and geese from the Arctic into Central Valley wetlands. Several million waterfowl congregate briefly around the Klamath Basin from mid-October until mid-November. Here they rest and fatten until cruel winter storms push them frantically southward into the Central Valley. Visiting Klamath Basin during this period is unforgettable. The birds mill about, calling loudly and jostling for position, as more waterfowl arrive each day. Huge flocks take to the air and land nearby, until one day all launch into flight and surge southward to their final wintering grounds.
Another way to celebrate migration season is to visit the Sandhill Crane Festival in Lodi on November 4-6. Now in its eighth year, this popular festival coincides with the arrival of sandhills in the Central Valley. Large numbers of cranes gather around Lodi and are easily seen on tours to nearby Isenberg Reserve and beyond. Activities include crane viewing, art shows, talks, contests, and more. For details, see www.lodichamber.com/cranefestival.asp.
Fall triggers another migration of sorts underfoot. Prompted by chilly mornings and shorter periods of daylight, caterpillars of the Isabella moth begin seeking tufts of grass, logs, and rocks to hide beneath for winter. Better known as woolly bears, these caterpillars have broad bands of black and rusty brown hair that many people believe predict the severity of the coming winter. In fact, the caterpillars don't predict the weather as much as react to it. Their brown bands increase in width with each molt, so if cold weather arrives early, they will start hibernating while their bands are still narrow. But whenever there is a long, warm fall, their bands have time to grow.
David Lukas leads natural history tours and programs in the Bay Area. He can be reached at david@naturalists-in-action.com |
