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Silence of the songbirds. "Nearly half a century ago, Rachel Carson warned us of the grim plight of songbirds, sparking an uproar that led ultimately to the banning of DDT. In Silence of the songbirds, Bridget Stutchbury makes clear that the danger migratory songbirds face are greater than ever. Her book is an eloquent plea on behalf of songbirds, and also gives practical suggestions on things we can all do to help - for the good of the birds as well as the human race." (Tim Gallagher, author of The Grail bird)
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One way to estimate the total amount of bird mortality, the size of the iceberg if you will, is to carefully look for casual-ties in a field before and after treatment with a pesticide, through even the most thorough workers will miss some birds and scavengers will eat up much of the evidence before workers get there. Pierre Mineau, a research scientist with Environment Canada, reviewed field studies on carbofuran done in the 1980s to estimate bird mortality after US corn fields were treated. Carbofuran is applied to fields as granu-les that stay on the surface of the soil, and birds eat them. At that time about six million hectares of corn fields in the United States were treated with carbofuran. Carbofuran ranks among the top four pesticides known to have caused large-scale bird kills, and a single carbofuran granule is enough to kill a small bird. Mineau’s study shows that while carbofuran was in wide use during the 1960s and 1970s it must have killed hundreds of millions of songbirds. The body count after a single carbo-furan treatment was astounding, and ranged from 22 birds per 100 hectares in Iowa to a shocking 850 birds per 100 hectares in Utah. The horned lark, a grassland songbird that frequents corn field, was the most common victim. To esti-mate the total number of birds actually killed, we have to take into account the number overlooked by the search teams and the carcasses taken away by scavengers. To find out how good the searchers were at spotting victims, dead birds were scattered in a field, then the search teams were sent in to do a count. The search team found only six out of every ten "planted" dead birds. In corn fields in Maryland, researches placed a known number of songbird carcasses in a field and returned the next day to see how many were missing. Three quarters had been removed by scavengers, so would never have been found by search teams. When Mineau corrected for both the birds missed by search teams and the ones eaten by scavengers, he found the actual death rate was estimated at 305 birds per 100 hectares in Iowa and over 1,000 birds per 100 hectares for Illinois and Utah. With this best estimate of the true rate of bird mortality, the total number of birds killed in corn fields in the late 1970s would exceed eight million birds each year. Bridget Stutchbuty: Silence of the songbirds, Walker & Company, New York, 2007. |
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