River of Raptors
One of the world's greatest wildlife spectacles takes place every autumn as millions of hawks and other soaring birds funnel through Veracruz, Mexico, where a pioneering program aims to keep them flowing for millennia to come.
The region has an urgent need for land stewardship, says Elisa Peresbarbosa, conservation subdirector at ProNatura Veracruz. "The trends are disquieting." These flatlands owe their glorious chartreuse color largely to chemical-intensive sugarcane, which covers 75 percent of the irrigated plain. Most of the wildlife habitat in the migration corridor now lies in the foothills and canyons of the southern arm of the Sierra Madre, the Sierra Manuel Diaz. But a long-term drought is rendering farming and ranching in the foothills less and less viable and has intensified the emigration of young men to the north--"Veracruz's biggest export commodity," locals joke blackly.
"Landowners see no options other than to cut a little more forest and run more cattle," Peresbarbosa says. "It feels to them like it will improve the situation. But . . ." She shakes her head. The problem is not so much food for the winged migrants, Peresbarbosa says--amazingly, many hawks and vultures soar so efficiently they appear to be able to fast for weeks at a time. But the birds do need significant stands of trees in which to roost overnight. As pasture marches farther up into the foothills it forces raptors to divert inland, off the flyway, to find such perches.
For their part, farmers and ranchers are also feeling the consequences of deforestation. One gnarled old fellow spoke up at a ProNatura-sponsored town meeting to lament that he'd cleared around a spring and the spring had returned the insult by running dry for the first time ever. In answer a state official, Flora Zitacuaro, outlined government assistance for watershed protection and invoked the universal benefit of forest. "People need the same things birds do," she said.
Hawks migrate?" marvels a backpacker, gazing bemusedly at some ProNatura outreach posters.
Boy, do they. As summer's end nears, they drain down through North America like water from a gigantic watershed. What's more, these iconic, solitary hunters migrate together, rivulets of lone birds trickling into small bands, small bands flowing into bigger ones. They lay up in the grasslands of South Texas and northern Mexico, pooling in immense mixed flocks, fattening themselves up and awaiting propitious conditions--hot days with little or no rain. Then they lift off and push on, by the hundreds of thousands.
New World raptors migrate to and from roughly the same places New World songbirds do, and for the same reason--so as not to starve during northern winters. But the two employ radically different strategies. Songbirds tend to travel at night, to avoid predators, it's thought, and to take advantage of the heat-wicking cool and relative calm of night air. They rest and eat by day, so they can burn up the miles by night, beating their small wings steadily hour after hour, in energy-intensive, powered flight. Though a few songbird species skirt the Gulf of Mexico, migrating along the coastal plain, most take the heart-stopping shortcut across the open water, covering 500 miles in a single, epic, 18-hour flight.
Hawks and vultures travel exclusively by day, over land, exploiting the turbulent currents of sun-heated air, their wings more or less fixed. As befits solar-powered birds, they keep bankers' hours.
In San Juan Villa Rica, a dusty hamlet on Sierra Manuel Diaz's outflung elbow, farmers have decanted their milk into the urns in the cheese factory pickup truck, in the shade of the blue-painted fig tree that marks the village center. Miriam Lerma Lizarraga and Yocelyn Ramirez Gonzalez, from ProNatura, are going door-to-door this morning, spreading the gospel of environmental awareness.
"Hawks! They steal my chickens! That's why we have to kill them!" roars a bare-chested, barrel-bellied man lounging in a plastic chair on an open patio. It's not an unusual sentiment among ranchers, says Lerma Lizarraga, if somewhat more emphatically expressed.
"The migratorios don't eat chickens. They just look for trees to rest in as they make their way down the isthmus," she explains calmly.
"We see clouds of them," says a stout woman with a seraphic smile, sorting limes in her aproned lap. "They go around and around like this"--she stirs the air in front of her with lime-filled hands, vividly conjuring up a rising gyre. Instinctively all heads turn to the sky.
That's exactly how they do it, says Robert Templeton, a retired physics teacher from New Mexico. Birding here with his wife four years ago, he witnessed a colossal day--640,000 birds flooded through the bottleneck. Templeton now returns to volunteer for ProNatura every fall. The photographer Ewan Burns and I have shanghaied him in our little white rental car and cruised up to Villa Rica hoping to get closer to soaring hawks.
It's after 11 a.m. now, and the sun is frying the coastal plain. Sunlight is heating the surface at different rates, according to how reflective the ground cover is. Hotter air expands, becomes lighter; plumes of hot air called thermals begin to rush upward.
Thermals start at the ground, Templeton says. "So as the morning progresses roosting birds will be watching one another. At some point a bird will take a glide to another tree. And then one will go up and make a little loop and come down. So they keep doing this. And then the next thing you know, someone goes up and they don't come down. And they all tend to go pretty quickly at that point."