The Canadian Peregrine Foundation


ARTICLE 6  - Argentine Spray Kills Hawks From Canada
(by Peter Whelan)

Pesticides sprayed on fields in Argentina are killing tens of thousands of wintering Swainson's hawks that nest on the Canadian Prairies and the adjacent U.S. Great Plains.

A researcher from the U.S. Forest Service counted 3,909 dead hawks in a 50-kilometer square last week and estimated they represented between 20,000 and 40,000 dead. The count was incomplete, partly because scavenging vultures and caracaras were eating the bodies quickly.

The insecticide monocrotophos and other pesticides are being sprayed from aircraft and tractors to control grasshoppers in fields of alfalfa and other new crops. Hawks flying behind the tractors to seize flushed grasshoppers get sprayed directly, then eat more pesticide in the grasshoppers.

Scientists from Canadian and U.S. governments and universities are working with the Argentine environmental agency, INTA, to propose a change to less severe pesticides.

Research scientist Geoff Holroyd of the Canadian Wildlife Service in Edmonton said the situation needs urgent action, especially since the Swainson's hawks have been in decline for a decade in their main Canadian breeding grounds in Saskatchewan and Alberta. Nesting failures have explained part of the problem, but researchers have been puzzled and alarmed by a further downward drift.

"I think this is comparable to what happened to the peregrine falcon inŒthe 1950s and 1960s. Hopefully, we have caught it in time," Mr. Holroyd said.  "This went to the Environment Minister's desk, and he approved action within 24 hours."

The anatum race of peregrines was all but wiped out by pesticides in eastern North America three decades ago and is just coming back now with the help of planting programs. Mr. Holroyd is chairman of the Canadian committee working to rebuild the peregrine population.

Environment Canada is funding field work by INTA, and Canadian farm experts are to offer advice about pesticides. "It is too late to do anything this year, but we hope for a solution by next winter," Mr. Holroyd said.

The Swainson's hawks will leave Argentina at the end of February and spend two months migrating north.

The big, dark-chested hawk is a familiar sight soaring over the Canadian Prairies on uptilted wings, like a vulture. It raises its young largely on Richardson's ground squirrels but eats many insects after migrating in large flocks to the wintering grounds on the South American pampas.

The Canadian population is estimated at 40,000 to 100,000 in a world population of 350,000 to 400,000. Canadian birds were inordinately represented in the Argentine deaths. Of 12 leg bands recovered, nine were from Alberta and Saskatchewan hawks. Two Alberta hawks tagged with satellite transmitters are both in the danger area.

The study area is at the junction of the states of Cordoba, Buenos Aires and La Pampa. Cattle ranching used to dominate, but irrigation recently opened the area to a variety of crops. This is only a small part of the winter range of the hawks and a small part of the cultivated farmland. "We don't know how far this problem extends," Mr. Holroyd said. Ninety per cent of the killed hawks were adults. The separate winter range of immature birds is not known.

Monocrotophos is an organic phosphate insecticide that is fast-acting and highly toxic to birds and animals. It kills insects either on contact or when taken in with crops. It is no longer sold in the United States and was never registered in Canada.

At worst, the Argentine toll would represent 5 per cent of the world population and half the Canadian population, Mr Holroyd said.  "This appears to explain the decline in this hawk. We also speculate that secondary effects of the pesticides could be reducing nesting success of the birds when they return to Canada."

Concern that Argentine pesticides were hurting migrant North American hawks appeared in birding literature as long ago as 1968, but there were no specifics. The first solid evidence came last year when 700 Swainson's hawks were found dead in the same area, apparently from pesticide poisoning.

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