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Mountains and Marshes. David Rains Wallace
Читать онлайн.Название Mountains and Marshes
Год выпуска 0
isbn 9781619026735
Автор произведения David Rains Wallace
Жанр Биология
Издательство Ingram
Lincoln designated four North American flyways—the Atlantic, Mississippi, Central, and Pacific. They were shaped like tornadoes, wide in the boreal and arctic areas where many migratory waterbirds nest, then narrowing into migration routes through the United States, Mexico, and areas south. (Most North American migrants winter in Central America and the Caribbean, although some reach South America and a few, like Swainson’s hawks, fly all the way to Patagonia.) Lincoln acknowledged that there was a lot of crossing from flyway to flyway, but aside from their soft edges, he considered them real biological entities. After World War II the new Fish and Wildlife Service came to regard them as such, making them the basic administrative units for hunting regulations and refuge management.
Lincoln’s work definitely contributed to migratory bird management. Since his death in 1960, however, ornithologists have largely discarded flyways as biological entities. One biologist who studies songbirds gave them a scathing review, calling them “misleading . . . hopeless, bogus . . . like saying the earth is flat . . . a disservice to science.”
“Small birds are broad front migrants,” he said. “They inherit an ability to fly a certain distance in a certain direction, and they don’t care if there’s an ocean or a mountain range in the way. Where’s the flyway in that?” He grudgingly granted flyways limited usefulness for counting and managing geese, swans, and cranes but doubted their value for ducks, which he said fly in inherited directions and may change breeding grounds when following new yearly mating partners.
Most ornithologists agreed in milder terms, acknowledging flyways’ significance as an administrative tool for managing species that follow strongly established migration routes. In his authoritative Ducks, Geese, and Swans of North America, Frank C. Bellrose called them “useful geographic terms . . . and political units” and cited some cases in which waterfowl migration “fit neatly into a flyway.” But: “Flyways fail to define the passage of waterfowl because they cover too extensive an area and do not delineate movements of waterfowl that are lateral to a north-south direction.”
Some avian groups, including most of the Bay Area’s seabirds, definitely transgress the flyway concept. Brown pelicans nest on islands off southern California, then wander up and down the coast looking for food. White pelicans nest on inland lakes, then move to the coast for food. Some gull and tern species also go east to lake breeding grounds after wintering here. Other gulls and terns nest here, while some winter here and then fly north to breeding grounds. Common murres and pigeon guillemots that nest here may fly north for the winter as well as south. The notoriously endangered marbled murrelet spends winters feeding at sea and summers nesting in redwoods or Douglas firs.
Even with conventional migrants, flyways are more about administration than conservation: it’s the ground and water where birds breed and feed that need to be protected, not the air they fly through. Lincoln wouldn’t find much banding information on pintails and widgeons at Lake Merritt these days. In his time, and until the early 1960s, several thousand of these dabbling ducks visited the lake in the fall. A few dozen visit it now, because there are a lot fewer ducks. Most migratory bird populations have declined steadily as habitat has disappeared.
Yet the federal government did little for Bay Area migratory bird habitat until the environmentalist uprising of Earth Day, 1970. The first federal refuge on the Bay came in 1972—Don Edwards San Francisco Bay National Wildlife Refuge, named for the congressman who helped push it past the growth boomers and through the legislature. San Pablo Bay NWR followed in 1974, through a similar process. (The Fish and Wildlife Service finally replaced the Coast Guard at Farallon NWR that year.) In 1980 the Bay Area got the only federal refuge established to protect endangered plants, Antioch Dunes NWR. A refuge established in 1992, 339-acre Marin Islands, protects the largest heron and egret rookeries in the Bay Area, although most of its acreage is under water.
Together, the four refuges on the Bay itself add up to somewhat more than fifty thousand acres of wetlands and other habitat. This protection represents massive efforts on the part of the local public. When Congress established San Pablo Bay NWR, for example, it comprised 175 acres, and local government had approved a 1,585-acre commercial and residential development nearby. One of the reasons for establishing the refuge was that 80 percent of the canvasback ducks in the Pacific Flyway were known to feed and rest on San Pablo Bay wetlands. Thousands of houses, apartments, and office buildings obviously would have impacted that. Citizens took government to court to force an environmental review and—with the help of then congressional representative Barbara Boxer and the U.S. Land and Water Conservation fund—finally saved the 1,585 acres by buying the land from a Japanese corporation for $7 million.
Yet the refuges don’t represent a massive area considering that hundreds of thousands of wetland acres disappear from the continental United States every year. Of course, state, regional, and local parks also protect Bay Area wetlands, and conservationists led by David Brower, Edgar Wayburn, and Congressman Phillip Burton saved much migratory bird habitat when they pushed the United States to establish Point Reyes National Seashore and Golden Gate National Recreation Area. The restored marshes and riparian woodlands there are a revelation. But, considering the Bay’s international significance as a unique ecological system (UNESCO designated it a biosphere reserve in 1988), one might think that the world’s richest nation could do more.
Whatever the biological significance of Lincoln’s avian nations, it’s hard to get much sense of the Bay as more than a “stop on the flyway” from the National Fish and Wildlife Service refuges here. In the Central Valley refuges, the surrounding farmland’s open horizon gives a certain feeling of integrity, albeit a truncated one. The Bay Area’s refuges can seem like museums because the surrounding artificial environment is so pervasive.
When I visited San Pablo Bay one late spring day in 2014, the lone hiking trail to the marshes at Lower Tubbs Island led past huge hay fields and spoil banks for most of its length. At Tubbs Island, the trail became impassible because a stretch had collapsed into the marsh and the NFWS lacked the money to fix it. This being the off-season, waterbirds were scarce anyway, aside from a few mallards and egrets. As I walked out to where the trail had collapsed, a buzzing roar like a swarm of giant insects erupted from the north. Looking that way, I saw dark objects zipping up a hillside like giant bees scurrying around a hive. It was like a 1950s atomic mutant movie. Then I remembered— it was the Sears Point Raceway.
The South Bay around Don Edwards Refuge is more urbanized than San Pablo Bay, but its marshes seem less constricted because more public facilities exist. When I walked the trails around the visitor center a few days after my San Pablo hike, the warehouses, hotels, and technology parks to the east seemed to fade on the horizon, although they’d looked real enough as I drove in (albeit with surprising numbers of empty parking lots and FOR LEASE signs). I saw more birds than at San Pablo—shoveler ducks as well as mallards, gulls dipping into salt ponds, swallows nesting on an old hunting shack—but the only spectacular sight was a flock of white pelicans, and they weren’t flying over the refuge but over Coyote Hills Regional Park to the north.
A wildlife kiosk on one of the restored Don Edwards marshes referred tersely to the flyway concept: “On the west coast, most birds migrate between their summer and winter homes along a migration corridor known as the Pacific Flyway.” A kiosk on the impassible trailhead at the San Pablo Refuge reflected the concept’s present status more appositely. One panel had a block of biological boilerplate about the flyway superimposed on a color blowup of a black-necked stilt (the only one I saw that day). The type was illegibly sun-bleached—a fading screed of ornithological anachronism.
There would have been more birds if marshes and riparian woodlands, instead of hay fields and buildings, had stretched the horizons. When they did, the Bay must have been more than a way station for many shorebirds and waterfowl. There was a lot more water to produce food for them, and thus more nesting. The restored wetlands at Point Reyes support summering coots, grebes, rails, green herons, blue herons, bitterns, and wood ducks, as well as egrets and mallards.
If Frederick C. Lincoln had conceived his flyways in the sixteenth