Docent Circle: Field Notes Week of 2005-04-18

Back East, the ever-popular and colorful American goldfinch breeds in July to take advantage of ripening grass seed crops. But in California's unique Mediterranean climate, grasses mature earlier in the year and goldfinches correspondingly shift their nesting season as early as May. Sometimes referred to as wild canaries, brilliant yellow males with black foreheads launch into lively trills and twitters. Meanwhile, females weave cup-shaped nests so fine that they will hold water in a rain. The four to six eggs hatch in about a week and a half, just in time for the fledglings to get their first beakful of nutritious seeds. Watch for the gregarious goldfinches all over the Laguna, in grassy areas and in large flocks feeding on weeds of chicory, thistle and other plants.

Great Blue Herons, Great White Egrets, and Snowy Egretshave already arrived to claim their place in the Laguna heronries. The male Blue Herons were the first to arrive. While waiting for the female to arrive, they defend the site from other males and display their breeding plumage, stretching and fanning their decorative aigrette nuptial feathers. Courtship dances commence as the female takes up residence on the nest: the male offers her a twig, the female takes the twig from the male's beak and carefully places it in the nest while the male watches. Then the ritual is repeated when the male flies off to find another perfect stick.

For most of the year, vernal pools are dry, grassy depressions in the earth. But when winter rains soak our summer-parched soil, these poorly-drained bowls fill with water and burst into life. Though vernal pools dot California's grasslands, they're found almost nowhere else on Earth. The pools host myriad plant and animal species that have evolved speedy life cycles designed to take advantage of the brief wet season. Among these are small crustaceans known as fairy and tadpole shrimp, which hatch from dormant, buried eggs just a few days after pools fill with rain. Fairy shrimp are inch-long lacey animals which glide upside down with graceful, rhythmic beats of their two rows of dainty legs. Walnut-sized tadpole shrimp sport a hard, rounded shell and plow through mud on pool bottoms. Though the shrimps' hardy eggs can lie dormant for years and are spread with wind-borne dust, many species have landed on the endangered species list because their habitat -- California's rolling hills and flat valleys -- is rapidly giving way to development.

When trees and bushes burst into new growth during the warming days of spring, the cambium (a layer of cells just beneath the bark) also begins to grow rapidly. As the cells divide and expand, they loosen the bark's grip on underlying wood, a condition known as bark slip. Native California basketweavers, orchardists, and loggers take advantage of this phenomenon. Basketweavers collect young twigs and shoots of willow, redbud, hazel, gray pine, sumac, and big leaf maple during barkslip. After peeling away the bark, the weavers use the smooth, white, and supple sticks for the foundation (warp) of their baskets. The slipping period can be brief --a week or ten days for hazel, for example. Basketweavers who miss the harvest in one area can find good material further north or at higher elevations where spring arrives later. Fruit tree growers have to wait for bark slip to use two of the most common grafting techniques: budding and bark grafting. And builders who work with pole construction like to harvest Douglas-fir and incense cedar in the spring when they can practically peel the bark from logs with their bare hands.

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