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SILENCE OF THE SONGBIRDS

How We are Losing

the World's Songbirds

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and What We Can Do

to Save Them

By Bridget Stutchbury

HarperCollins, 243 pages, $36.95

About this time of the year, throughout the 1940s, weather radar operators would observe huge blips on their radar screens, large patches covering vast areas, sometimes whole states, that were not storms. They called these mysterious images "angels," and only later discovered that the angels were in fact enormous flocks of migrating songbirds, hundreds of millions of them, each individual bird reflecting a radar echo like a large drop of water. Today, Bridget Stutchbury writes, although there are still millions of migrants, "there is good reason to believe that the angels are slowly falling from the sky, dwindling in numbers year after year."

In Silence of the Songbirds -- the echo of Rachel Carson's epoch-making Silent Spring is deliberate -- Stutchbury, a biology professor at York University who has been studying songbird migration for more than 20 years, charts the decline, pinpoints its various causes and suggests ways we can slow down the rate of the birds' disappearance. Her book is a thoroughly researched and elegantly written call to arms.

In the past 40 years, more than two dozen species of songbirds have suffered continent-wide decreases in population, up to 50 per cent in some cases. These include such familiar locals as the eastern kingbird, the barn swallow, the wood thrush, the Baltimore oriole, the rose-breasted grosbeak and the bobolink, as well as 10 species of warblers, three flycatchers and two pewees. This is no temporary dip, she warns: Species that were in trouble in the 1970s are in deeper trouble now, and new species are being added to the list with every field study.

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Some of the culprits are familiar. Much of the damage is being done in Central and South America, where most of our migratory songbirds spend the winter fattening up for the long trek north in the spring. "Since the 1980s," Stutchbury writes, "Latin American countries have been clearing about four million hectares of forest per year." In the past century, more than 300 million hectares of rain forest -- an area half the size of Canada -- were logged and turned into cropland. Environmentalists decry the cutting and burning as threats to species diversity and contributions to global warming.

Stutchbury adds that the rain forest is vanishing songbird habitat. She documents how poorly songbirds do in rain-forest fragments and scrublands, where birds take longer to store up enough energy for the spring migration, and are either too weak to make the return trip or arrive too late in the boreal forest to find mates and reproduce.

Our switch from shade-grown to sun-grown coffee on many South American plantations has also been hard on birds. Studies show that 43 species of songbirds winter in the forest canopy over shade-grown coffee trees, feeding on fruit and insects and contributing guano to the soil. Very few birds are found on sun-grown plantations, where only the occasional banana plant offers food for migrant Baltimore orioles.

Rain-forest soil makes poor farmland, and the use of fertilizers and pesticides is widespread and deadly to birds. "We are as hooked on pesticides today as we were in the 1960s," Stutchbury declares; we have just shifted our concentrations of chemicals southward, and import our food from farther away. She tells how, in 1995, researchers wanting to know where Swainson's hawks over-wintered found a farm in Argentina where 700 hawks were lying dead on the ground, having eaten grasshoppers laced with monocrotophos, a pesticide banned in North America but widely used in the south to kill langostas, or locusts. Costa Rica uses 45 kilograms of pesticides per hectare to grow bananas; Venezuelan rice farmers crop-spray with parathion to kill seed-eating dickcissels. During the 1970s, when carbofuran was used in U.S. cornfields, it killed eight million birds every year in Utah alone, and carbofuran is still one of the top 10 pesticides used in Latin America.

Not all the blame can be placed in Latin America, however. Deforestation is prevalent in North America, as well, and migrating songbirds struggle to find suitable resting and feeding sites along their flight routes. They also have to navigate around skyscrapers left lit up during the night, which the birds mistake for stars. (Toronto's Fatal Light Awareness Program, FLAP, has been collecting dead songbirds on Bay Street sidewalks for years, and lobbying building owners to turn off the lights during migration season, with only partial success.) And when exhausted birds land to rest during the day, they have to contend with rats and ring-billed gulls as well as other, less natural, predators, such as North America's 70 million feral cats. In fact, with so many obstacles in their way, it's a wonder so many songbirds survive at all. Since the 1960s, we have lost only 2 per cent of songbird species, although population numbers among the survivors are down 30 to 50 per cent.

Birds are more than colourful curiosities. They play vital roles in the greater ecosystem. It's ironic -- or rather tragic -- that we use insecticides on our crops that end up killing insectivorous birds. Some rain forest trees have evolved a dependence on birds to disperse their seeds farther than wind or water would carry them. On a more philosophical plain, Stutchbury notes that when we lose forests we not only lose songbirds and plants and other animals, "we also lose history. The evolutionary forces that led to these unique species are an irreplaceable piece of the history of our planet, and will never again be repeated."

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Songbirds, Stutchbury warns, are our canaries in the mineshaft. Like Rachel Carson in the 1960s, Stutchbury is issuing an early warning that we ignore to our peril: "We have learned the hard way that when birds begin disappearing, we may be next."

Wayne Grady's most recent book is Bringing Back the Dodo: Lessons in Natural and Unnatural History. Each May, he travels to southwestern Ontario to await and celebrate the return of migrating songbirds.

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