Accord Is Reached To Recall Pesticide Devastating Hawk
AN agreement between an international chemical company and environmentalists may help reduce poisoning that has killed thousands of  hawks on the pampas of Argentina in  recent years.
The deaths of members of a broad-winged species called Swainson's hawk were caused by a highly toxic pesticide used by farmers to fight grasshopper infestations. Even now the hawks are working their way south from the North American grasslands to Argentina.
The pact commits Ciba-Geigy Ltd. of Basel, Switzerland, to remove the chemical, known as monocrotophos, from the market in the agricultural area 300 miles west of Buenos Aires where most of the world's Swainson's hawks congregate during the South American summer. The company also agreed to buy back stocks of monocrotophos in the hands of distributors, applicators and farmers. Ciba-Geigy, which makes one-third of the monocrotophos sold in Argentina, said it would encourage several other producers of the pesticide to take similar steps.
The agreement was disclosed yesterday by the American Bird Conservancy, a Washington-based advocacy group representing 56 environmental and ornithological organizations. Gerald Winegrad, its director of government relations, said the conservancy's goal was to convince the company to take the chemical off the market worldwide.
While the Argentine Government recently prohibited the use of monocrotophos for grasshopper control  and banned all uses of the chemical on the alfalfa fields where many of the Swainson's hawks forage, scientists in the United States and Canada worry that farmers whose crops are under attack by the insects will continue to use existing stocks of the poison. Maria Elena Zaccagnini, a  wildlife biologist with Argentina's National Institute of Agriculture Technology, said climatic conditions were right for 'an immense grasshopper population during the coming season.'
Argentine agencies and Ciba-Geigy have also started a program to inform pampas farmers about the threat pesticides pose to the hawks.  But Dr. Pierre Mineau, head of the Canadian Wildlife Service's pesticide section, expressed concern that time was running out for farmers to return monocrotophos supplies or buy substitute chemicals before mid-November, when the birds arrive in the area. And Ms. Zaccagnini said there was no evidence yet that chemical companies were removing monocrotophos from farm supply stores.
Swainson's hawks nest on prairies, plains and deserts west of the Mississippi River, usually from May to August. The species' continent-wide population is estimated at 400,000.  Until recently, biologists were puzzled by a decline in the bird's numbers in the Canadian prairie provinces and in several far western states.
Early in the breeding season, Swainson's hawks hunt rodents,  mainly the ground squirrels that can be abundant on arid western grasslands. But Brian Woodbridge, a biologist with the Klamath National Forest in Northern California who has studied the raptor for the last 13 years, said the birds 'delay nesting so their young fledge in August when grasshopper outbreaks occur.'
Little was known about the migration of the species until two years ago, when Mr. Woodbridge used satellite telemetry to follow two Swainson's hawks from the Butte Valley in California, north of Mount Shasta, to Argentina. There the biologist found huge flocks of hawks soaring over alfalfa and sunflower fields during  the day and roosting at night in eucalyptus groves planted near ranch buildings. Mr. Woodbridge also found  hundreds of dead hawks, and a farmer told him the birds had died after a field next to their roost was sprayed.
Last winter Mr. Woodbridge returned to the pampas with Michael Goldstein, a graduate student at Clemson University. They counted 4,000 dead Swainson's hawks at four sites and estimated that 20,000 of the raptors had died from aerial and ground spraying of a pesticide that forensic evidence later confirmed to be monocrotophos. Some of the birds were killed by direct exposure to the spray, and others by eating poisoned  grasshoppers, Mr. Woodbridge said.
Monocrotophos, one of a group of agricultural chemicals known as organophosphates, is marketed to control a variety of insects, but it is neither manufactured nor used in the United States. The pesticide is banned in Canada.
Dr. Michael Hooper of Clemson's Institute of Wildlife and Environmental Toxicology, said Swainson's hawk 'may be very sensitive to organophosphates.' Dr. Hooper noted with concern that another, less toxic  organophosphate pesticide was being recommended as a replacement for grasshopper control.
He said an extensive monitoring program this winter involving scientists from Argentina and North America and nearly 30 satellite-linked hawks 'will go a long way to help us determine whether the species' problem is basically with monocrotophos.'