Protecting songbirds, their familiar terrain

Refuge: Biologists hope to preserve areas of Texas and Louisiana to ensure that migrating songbirds have a place to rest.

May 12, 2002|By Heather Dewar | Heather Dewar,SUN NATIONAL STAFF

BRAZORIA COUNTY, Texas - In springtime, this is where the angels are.

In the 1950s when weather radar first came into common use, Gulf Coast radar operators along the Texas-Louisiana border were puzzled by strange patterns. Just after dusk on April and May evenings, mysterious circles suddenly appeared on their screens, expanded quickly into huge white clouds, then just as quickly vanished.

Not knowing what to think, the radar operators called them "angels."

Scientists now know that the angels are migrating birds - 29 million of them - in every shape, size, color and song.

After a perilous journey of 400 to 600 miles across the Gulf of Mexico, most of the migratory songbirds of the Eastern United States make landfall in southeast Texas and southwest Louisiana. Hungry, thirsty, tired and hunted by high-flying predators, they seek the shelter of forests.

But in a landscape dominated by oil refineries and chemical plants, cattle ranches and subdivisions, havens are scarce. And scientists say that is a main reason why the birds' songs of summer are fading in many parts of the country. The birds are also bedeviled by forest clearing in the United States and in their wintering grounds in Latin America.

Radar studies show that the number of migrants passing through this area declined by nearly half from 1965 to 1989.

"If there's no place to breed, if there's no place to stop over, they're gone," said Cecilia Riley, director of the Gulf Coast Bird Observatory in Lake Jackson, Texas.

Migration experts say the odds are good that any Baltimore oriole building its nest this morning in a Central Maryland wood lot came ashore near the Texas-Louisiana border in the past few weeks. Most likely, so did the yellow warblers singing "sweet, sweet, sweeter than sweet" as they build their nests in thickets along the Patuxent River. And indigo buntings catching insects in an abandoned Eastern Shore pasture probably crossed the same stretch of shoreline.

Now the federal government, the state, private conservation groups and land owners are trying to create a haven for these and about 265 other varieties of birds that fill the nation's back yards with color and music.

Assembled from the remaining scraps of southeast Texas' forests, it is known collectively as the Columbia Bottomlands in honor of a nearby town that was Texas' first capital.

"Even though it's fragmented, those are the most important fragments on the Gulf Coast," said Sidney Gauthreaux of Clemson University, who has been using radar to study bird migration since the 1960s. "If we had to pick a place in all of North America that is most important for these birds, it probably is the upper Texas coast and southwest Louisiana."

Scientists think the migrants take flight from Central America just after dark, relying on night to conceal them from predators and on late spring winds from the south to help carry them on the shortest route across the sea. The tiny creatures, in most cases weighing half an ounce or less, might lose a third of their body weight and burn up muscles on the grueling 18- to 30-hour trip.

Under ideal conditions, uncountable thousands succumb to fatigue and drown.

But occasionally stormy weather forces the travelers to fight a head wind and forces them to concentrate in a large cluster - a phenomenon known as a fallout.

As soon as they reach land, the exhausted birds fold their wings and dive for the nearest clump of woods, descending in a bright blur like a rain of jewels.

"It can be just incredible," said ornithologist Wylie Barrow of the National Wetlands Research Center in Lafayette, La. "Literally every vine tangle and every bush can be covered with birds. On a single branch of a hackberry tree, you can see half a dozen species of warblers, a couple of tanagers and a thrush, and the next branch will be just as dense" with fluttering throngs of topaz, garnet, sapphire, emerald and gold.

Seeking food, rest and shelter from hungry hawks, the tired migrants alight in the densest, most insect-rich forests they can find. Their choices are few.

Over the past 100 years, the hardwood forests that once covered the soggy "bottomland" along rivers' flood plains have been cleared for farming, timber and subdivisions. The only large woodlands remaining are the Atchafalaya Swamp in Louisiana and the Columbia Bottomlands, Barrow said.

"The Columbia Bottomlands is really the most significant in my mind," Barrow said. "I really don't know of another extensive old growth forest anywhere in the South. They're all gone."

The forests, dominated by oaks, pecans, sweet gums and cypresses, once covered a thousand square miles in a broad fan south of Houston. But only about one-fourth of that remains, said U.S. Fish and Wildlife Service biologist Michael Lange, coordinator of the Columbia Bottomlands project.

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