| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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NATURALIST'S ALMANAC What to Look For This Spring David Lukas April
A sure sign that spring has arrived in the deserts of the Southwest is the steady cooing of white-winged doves echoing through streamside thickets and suburban woodlots. Arriving in early to mid-April along the lower Colorado River Valley and throughout eastern San Diego County, these grey-brown birds with striking white wing margins quickly take up residence in stands of densely foliaged trees. Here they find respite from vigilant predators and the sharp beating eye of the desert sun. After building crude stick nests, hardworking pairs will settle down to raise two to three broods, each containing several chicks. Being one of the few desert inhabitants that don’t obtain enough water to live from the food they eat, white-winged doves must journey twice a day in search of liquid. They gather by the hundreds around waterholes in the early morning and late afternoon waiting anxiously for one brave enough to fly down for the first sip. Few people realize that this familiar animal is only a recent arrival in California; it followed agriculture and ornamental lawns into the Imperial Valley in the early 1900s.
The Mediterranean climate of the Central Valley and Coast Ranges pushes animals and plants into a flurry of spring activity before the crinkling heat of summer envelops the landscape. Among these is the gentle California tiger salamander. Only recently recognized as a separate species, it has generated intense controversy over the protection of its critically threatened populations. With the first soaking winter rains, adults lay their eggs in seasonally ephemeral grassland ponds. Tiger salamander larvae must metamorphose fast, before their natal pools vaporize in the summer sun. Leaving the water as two to three inch replicas of the adults, the juveniles find safety in moist rodent burrows where they slowly grow in size. May
If the early landscape of California’s Central Valley could have been likened to the Serengeti, it would surely be due to the vast herds of pronghorn antelope that once roamed this flower-studded savannah. Now primarily restricted to the high, cold plains of the Modoc Plateau in northeastern California, these antelope survive in a landscape of sagebrush and junipers. Though they will grow to three feet at the shoulder and around 100 pounds, fawns start life as extremely precocial, five-pound bundles able to stand and suckle while still wet from the womb. Within an hour of birth, each fawn finds its own bedding site in the open prairie. There it will lie still for two to three weeks, hoping to avoid predators by remaining completely inconspicuous. So perfect is this strategy that three scientists once spent two hours unsuccessfully searching a tiny plot of ground where they had just witnessed a fawn bed down. On another occasion, a researcher using Labrador retrievers to find fawns by scent watched his dogs walk within feet of a fawn without noticing it. The antelope use a secret strategy to keep their young hidden. After a fawn suckles from its mother, it will urinate and defecate into its mother’s mouth to avoid creating a scent in its hiding place.
June
One of California’s prettiest aquatic plants begins its floral display this month. From floating mats of sixteen-inch-long heart-shaped leaves, yellow pond lilies bloom with flowers that look like yellow waxy floating cups. What are visible are mostly the broad sepals; the petals are nearly hidden by reddish stamens that form a ring around a huge, central, knob-like stigma. These distinctive flowers are often added to artificial ponds for aesthetic appeal. Whether the presence of pond lilies has a positive or negative impact depends on your point of view. On one hand they are important for many types of aquatic invertebrates, while their seeds are a rich source of food for waterfowl. However, pond lilies become quickly dominant and crowd out other aquatic plants with large floating leaves that cover the water’s surface.
Along the California coast, upwelling waters in June create the basis for a highly productive food chain. Renowned as circus seals, but actually highly efficient predators, California sea lions feast on schooling species such as anchovies, squid, and shrimp during this period. Diving to nine hundred feet deep and hunting with whiskers exquisitely sensitive to touch and movement, female sea lions catch a steady supply of food in order to produce fatty milk for their single pups. In a good year, with plenty of food and milk available, roughly 45 percent of a colony’s pups die; but during an El Niño event, this number climbs far higher. With only thin layers of blubber and fur, sea lions stay close to tropical or subtropical waters. Nearly all of California’s sea lions breed in large colonies on the Channel Islands.
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