Читать книгу Mountains and Marshes - David Rains Wallace - Страница 12

pelicans and pantyhose

Driving around Oakland’s Lake Merritt is misleading. The lake seems raggedly artificial, a run-down vestige of genteel Victorian landscaping. The lake does have an artificial side. It originated in the 1860s when Samuel Merritt—an early land developer—dammed a polluted tidal inlet to make a setting for mansions like one he was building. High-rises and apartment houses of a certain Raymond Chandler ambience replaced the mansions, although the city turned part of the north shore into a park. Yet a walk around the lake will show that it is not just urban decoration. It is still a working part of San Francisco Bay’s ecosystem, connected by a tidal channel to the San Leandro estuary. Bay waters still ebb and flow in it, albeit controlled by floodgates.

As I write, the first winter storms are passing through, bringing two phenomena that embody Lake Merritt’s connection to the Bay. First, storm sewers drain the summer’s accumulation of litter and grime into the lake, an extraordinary welter of plastic, paper, dead cats, torn underwear—everything imaginable—all filmed with an iridescent engine oil slick that swirls on the lake’s surface. Tides flush some of this out into the Bay and ultimately into the ocean, although the city has to clean much of it. Second, the storms bring flocks of migratory and/or marine birds to the lake, where they feed and shelter for the winter: ducks, grebes, phalaropes, gulls, pelicans, coots, egrets, and cormorants, among others.

But what do the birds eat in this welter of garbage and muck? They eat the products of a rich, functioning ecosystem, albeit a dirty one.

A look into the lake reveals the basic elements. Mingled with Styrofoam cups and Big Mac containers are sheets and strands of algae, the photosynthetic producers at the food pyramid’s base. During the warm seasons, algal blooms fill the lake, breeding disagreeable smells but also many small shrimp and other invertebrates. These feed small fish—mainly smelt and gobies—and they all reach astronomical numbers by October. A look into the lakeshore then will reveal smelt schools that shadow every inch of the bottom with their nervously darting bodies.

Algae, small invertebrates, and bacteria also feed large numbers of clams and mussels, and aquatic worms that live in white, limy cases and filter food from the water with bushy green gills. These organisms hide in the muck or attach to the lake’s stone margins, beer cans, or any other convenient substrate. Dead ones’ cases and shells cover the lake bottom.

In the fall, lowered temperatures and chemical changes in the water kill most of the algae, bringing famine and panic to swollen fish populations. Droves of small fish flee from larger ones into the shallows, where both become vulnerable to arriving birds. Sometimes schools suddenly die off, the bodies attracting large flocks of ring-billed and California gulls, which, lacking the skills of cormorants or diving ducks, ordinarily have to fish from the sidelines or rob other birds.

Lake Merritt’s odd mix of urbanity and biotic productivity make it a good place to watch fishing birds. Gulls and egrets are so used to joggers and roller skaters that they ignore them whizzing past, although they fly away if I walk too near them. But if I’m discreet I can often watch the birds stalking and catching fish from a few feet away.

The bird assemblage this fall was spectacular. A flock of brown pelicans—a dozen adults and half again as many juveniles—fed in the inlet between Kaiser Center and Lakeside Park. They sat in the water with their beaks tucked against their breasts, then somehow knew that a fish school was nearby and took off together, an ungainly flapping that quickly turned to graceful soaring just above the surface. Spotting fish, they dived into the water and opened their bill pouches, so they seemed to have veined balloons attached to their chests, thus trapping many small victims to be swallowed once the pouch was raised out of the water.

I doubt that the pelicans located the fish schools themselves. They were just the most conspicuous predators on them. Bonaparte’s gulls and Forster’s terns seemed more likely fish-finders, since they fly higher and dive nimbly to catch fish in their sharp beaks. I saw a Bonaparte’s gull dive into a foot of water below where I stood on the sidewalk and fly away with a several-inch-long goby I hadn’t noticed. Or perhaps the cormorants, with their underwater swimming skills, were the fish-finders that the other birds watched.

Whatever its workings, the birds’ feeding was definitely coordinated. When the pelicans, Bonaparte’s gulls, and terns left one part of the inlet for another, they were soon followed by the snowy and common egrets and the California and ring-billed gulls that had loitered in the shallows hoping to catch something scared by them. They were like spectators in tennis whites following a water polo game from one end of a swimming pool to another, with the splashing and shrieking of a country club crowd.

Fall is the most active time on the lake. In winter, rafts of ducks stay on the sheltered east side, but they’re quieter than the fall birds. They rest on the water with their beaks tucked under their wings. Equally idle cormorants often line the log boom that divides the ducks from the main part of the lake. But there’s still a lot going on. When the floodgates at the lake’s west end open to let in the tide, large fish appear in the current under the bridge. It’s hard to identify them, but they include sharks and striped bass.

In spring most of the birds leave for cleaner spots. Some try to nest on little wooded islands offshore from the Rotary Nature Center at Lakeside Park, but a colony of night herons that also nests there makes this difficult. The water clears and gets less littered after the rains taper off and before the algal bloom gets under way. This is a good time to watch the lake’s underwater doings, which can be as interesting as the birds’ fishing, if less spectacular.

I was walking beside the lake one bright warm day last spring when I noticed small fish darting individually among the algal clots that were starting to form. They weren’t smelt or gobies, so I stopped for a closer look and saw that some were a bright metallic blue, with ruby red bellies. They hovered over certain algae patches and chased away similar fish that approached. Sometimes they made quivering motions above the algae patches or burrowed into them.

I realized that they were male sticklebacks defending nest territories. Ethologists and biology teachers like sticklebacks because of their curious breeding habits. A male makes a nest in an algae patch by burrowing a tunnel. Then he lures cruising egg-laden females into it with a zigzag courtship dance. Once a female’s in the nest, he encourages her with nudging motions to lay her eggs, fertilizes them, and then chases her away. He repairs the nest and starts dancing to attract females again until he has a satisfactory egg collection, which he incubates by standing on his head in front of the nest and fanning oxygenated water into the tunnel with his pectoral fins. When they hatch, he anxiously guards the tiny fry, keeping them in a tight school. If one wanders away, he darts after it, catches it in his mouth, and carefully spits it back into his school.

I’d never seen wild sticklebacks, and I hadn’t expected to see them in downtown Oakland. Proceeding along the lakeshore, I saw bright blue males guarding algae patches every few feet—it was a stickleback city. I couldn’t stand and watch the whole breeding process since joggers and roller skaters would have knocked me into the lake if I had tried, but I was able to see the progress of the nests over the next few weeks. By the end of June, the algae clots teemed with thousands of tiny sticklebacks that were well protected in their filmy green chambers. One such school hovered over an open copy of Basic Math, which some liberated student had flung into the lake. I imagined the tiny fish doing their sums, instructed by a small whitish crab that sidled over the mussel shells on which the textbook rested.

—Berkeley Monthly, February 1980