Like most songbirds, the Swainson's thrush migrates alone and in the dark. Its nocturnal flights take it hundreds of kilometres from South or Central America to Canada each spring, then back again in the fall.
But last May, as the olive-brown birds made their way north through Illinois, a few of them had a escort: Princeton University biologist Martin Wikelski, racing after them in a 1982 Ford station wagon with a radio receiver sticking through the roof.
Each morning, Dr. Wikelski would catch one bird in a mesh net and attach a tiny radio transmitter to the feathers on its back. When the thrush took off that night, he and his team would give chase in their wood-panelled wagon, sometimes covering 600 kilometres before recapturing the bird at dawn for a blood sample.
"It is almost like that movie Twister, the crazy guys following the tornado. That's how we felt," Dr. Wikelski says.
The hardest part was knocking on strangers' doors at 6 a.m. for permission to find a bird on their property — one man brought out his gun. But Dr. Wikelski is driven by a sense of urgency: Thrushes, like many migratory songbirds, are in decline, and no one is sure exactly why, or how best to protect them.
SIGN OF SPRING
To most Canadians, migration is a spectacle that marks the seasons. We know spring is here, despite the snowbanks in much of the country, because northbound geese have begun to appear from the south, just as we knew winter was coming when we saw them flying the other way.
But many long-distance travellers — from the whooping crane and the red knot to sea turtles and the rarest of the world's large whales, the North Atlantic right — are in serious trouble. Over millions of years, they have been hardwired to undertake long journeys to survive. But these feats of strength and endurance are increasingly perilous in a world ever more congested and plagued by a changing climate.
The situation is so precarious that one of Dr. Wikelski's Princeton colleagues fears that migration, as a phenomenon, is slipping away.
A professor of ecology and evolutionary biology, David Wilcove is the author of No Way Home, a new book that outlines just how severely humans have disrupted animal-migration patterns. We have hunted and fished species into extinction, destroyed their habitat and blocked their way with roads and dams. Now, we are altering the climate.
Many species are in trouble — almost one in four mammals and one in eight birds — but those that migrate, Dr. Wilcove argue, deserve special attention because almost everything about them, from the hardships they face to the way their genes govern their behaviour, inspires awe.
Wildlife biologists, physiologists and geneticists are starting to solve the mysteries of migration, and many like Dr. Wilcove are so concerned that they are campaigning to have a $50-million satellite dedicated to tracking migration on land, in the sea and in the air.
BYE-BYE BIRDIES
No Way Home is both an ode to the spectacle of animal migration — the passenger pigeons that once blackened the skies over Eastern Canada, the bison that roamed the central plains of North America — and a lament for the millions of animals still on the move.
If you pick the right night in the spring or fall, Dr. Wilcove says, and a place away from the noise of urban life, you can hear the soft chirps and whistles of migrating songbirds overhead. He has been watching and listening to birds since he was a child. An avid birder by the age of 6, he remembers the adults on Audubon Society outings in his native Buffalo complaining that migrations were not what they used to be. As a young scientist, he collected evidence to prove that the old-timers were right, receiving his doctorate at Princeton in 1985 for his work on the disappearance of songbirds in the Eastern United States.
