Swainson's Hawk Migration

Insecticides kill hawks common to Prairies

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From The Star Phoenix Friday, Februaly 16,1996 Saskatoon, Saskatoon

BUENOS AIRES Insecticide poisoning has killed nearly 4,000 Swainson's hawks migrating from Canada and the United States, including some from Saskatchewan, to Argentina's grasslands since November, ecological groups said Thursday.

The birds, 90 per cent of them adults, were found in an area of just 50 square kilometres near the town of General Pico in the western province of La Pampa. Ecologists fear as many as 20,000 may have died countrywide.

"This is an emergency. The hawks were found in a very small area and yet they are known to inhabit at least four provinces," said Maria Elena Zacagnini of Argentina's National Institute of Agricultural Technology.

The hawks escape the north ern winter by flying more than 11,000 kilometres south to Argentina every November. They return north in early March to nest and reproduce.

The cause of death was almost certainly the pesticide monoctophos and other substances that Argentine farmers spray on alfalfa and sunflower fields to control grasshoppers, says a World Wildlife Fund report.

The WWF said 3,909 hawks have been found dead near Gen eral Pico, but warned that the figure could soar to five times that amount.

The hawks follow tractors to catch grasshoDpers disturbed by the passage ofthe machines. The insects contain a lethal dose of pesticides. The hawks also get contaminated directly by planes and air sprayers.

After 700 hawks died on Ar gentina's plains in 1994-1995, Canadian officials had satellite transmitters attached to the birds before they migrated south this year.

Of 12 leg bands recovered from the dead hawks, nine origi nated in Alberta and Saskatche wan. The other three were from Colorado, Idaho and California in the United States.

There are an estimated 350,000 to 400,000 Swainson's hawks worldwide. The Canadian popu lation is estimated at 40,000 to 100,000. Scientists from Canada, the U.S. and Argentina are working on ways less severe pesticides can be used.

Geoff Holroyd of the Canadian Wildlife Service in Edmonton said urgent action is needed since Swainson's hawks have been in a decline for a decade.

"I think this is comparable to what happened to the peregrine falcon in the 1950s and 1960s. Hopefully we have caught it in time."

Peregine falcons were almost wiped out by pesticides in east ern North America about 30 years ago, but have made a comeback thanks to efforts to re- build their populations.

Meanwhile, Alejandro Serret, conservation director at Ar gentina's Fundacion Vida Sil vestre ecological group, says northern hemisphere countries are at least partly to blame for the birds' deaths.

"They rightly cry foul when they hear of deaths caused by pesticides which are banned in their countries," he said. "But take a closer look and you'll see they're the ones exporting these killer substances to places like Argentina."

The Study

What: A study of Swainson's hawk migration from North American breeding grounds to South American wintering grounds.

How: 28-gram satellite transmitters were attached in backpack fashion on 8 Swainson's hawks. To save battery life, these transmitters are programmed to signal for 24 hrs at 3-day or 8-day intervals.

When: Two Satellite transmitters were deployed in 1994 and six in 1995. Transmitters should last several years if batteries can be replaced each summer.

Who: Seven biologists in California, Colorado, Cordoba(Argentina), Saskatchewan and Utah are supported by:

Why: Swainson's hawks are a common predator of rodents and insects on the North American Great Plains and the Pampa of South America. Special attention has been paid to Swainson's hawks because of recent deaths linked to insecticides. In recent years, breeding Swainson's hawks have been declining in Alberta and Saskatchewan. Only time will tell whether this decline is caused by low abundance of prey and thus temporary.

For more information, contact:
Joe Schmutz
joe.schmutz@usask.ca
(306)382-8964