Excerpted from Living on the Wind: Across the Hemisphere with Migratory Birds

On this hot midday, there is little birdlife within the monte  little life of any sort, since these Australian trees give off a toxin that kills plants growing beneath them, so the forests are empty of any sort of understory except for young eucalypts. Most of the birds prefer the wide-open grasslands, or the lower, scrubbier native acacias called caldin. But there is some activity. Chimangos scold and squeal, and spot-winged pigeons  bulky, gun metal-blue birds  flap explosively out of the branches. Tropical kingbirds machine-gun twittering calls as they zip from tree to tree, flashing saffron bellies and wing linings. The kingbirds are migrants, but their pattern is the reverse of the Swainson's hawk's. During the austral summer the robin-sized flycatchers breed across Argentina, but with the coming of autumn they migrate north, spending the midwinter months of June and July foraging along rivers in the Amazon basin. Likewise the fork-tailed flycatchers, which would be show-stoppers were they not so common on the pampas  slim birds the size of thrushes, black above and white below, with scissor-like tail feathers that may exceed ten inches in length. Forktails are among the most conspicuous birds in Latin America, found from southern Mexico to Patagonia, and both the northern and southern populations are migratory, using northern South America as their non-breeding grounds.

Swainson's hawks soar above a pampas
woodlot. In migration and during the
nonbreeding season in South America, the
hawks may form flocks numbering
in the tens of thousands.

As I walk down the rows of trees, a few Swainson's hawks lumber into the air, quickly catching thermals and riding high into the blue. I squat and shuffle along on my knees, searching for pellets, when my hand uncovers several old, matted feathers, still attached to a bit of dried bone. Gingerly, I brush away the covering of curled leaves, and find the complete skeleton of a hawk, partially mummified by the dry climate, its feet still clenched in the paralyzing grip of organophosphate poisoning. Looking more carefully now, I quickly discover that I am kneeling in a boneyard -- there are dozens, perhaps hundreds of skeletons in this corner of the monte, buried beneath just an inch or two of leaf litter, most still whole and articulated, held together by desiccated tendons. This is the same patch of woodland where Brian made his first gruesome tally two years before, where he found White 05 Left and more than seven hundred other dead Swainson's. I had seen the photographs of dead hawks, talked to Brian and others about their experiences, read the reports and news accounts. But only now, confronted with the weathered bones, did it really hit me just what was at stake.

Every day we wait in mingled hope and fear, carrying on the research while dreading the first call reporting a major kill. But as the weeks pass, Agustmn's phone remains silent, perhaps for several reasons. Unlike the drought of the previous year, this season is bountiful and wet; the sunflowers are eight or nine feet tall, capped with platter-sized seed heads, and the soybeans and sorghum grow almost while you watch. Farmers are more forgiving of insect damage when there is so much to go around, and the wet weather has both reduced the number of grasshoppers, and provided enough lush grass in road margins and waste places to keep them out of the fields. Few people, this year, are spraying for tucuras. By the end of the winter, in fact, the research team will have heard of only one small incident, involving just two dozen hawks  a dramatic change from the tens of thousands killed the year before.