May 07, 2009 - 04:30 AM
By Margaret Carney
It's happening all around us! What lots of people look forward to all year is at full throttle right now: a glorious spring migration.
Every night when the wind is from the south, tiny colourful songbirds arrive in Durham, dropping out of the skies at dawn to rest and feed. Some fly all the way from South America, bound and determined to reach our great Canadian forests to mate and breed.
For most of us, bird migration is an enigma. One day the woods are empty and silent; the next, they're filled with birds fluttering about and singing their hearts out. Where they've been all winter is a mystery. How they find their way "back home," travelling thousands of miles across mountains and seas, cities and deserts, is a marvel. Only in recent years are scientists figuring out bit by bit, through surveys, watches and radar, the remarkable annual journeys of neotropical songbirds.
A key piece of the puzzle has just been put in place by York University biology professor Bridget Stutchbury and her team of students. Two summers ago, they fitted tiny geolocator devices on the backs of 14 wood thrushes and 20 purple martins, hoping to trace their route. Amazingly, a year later they managed to retrieve those precious little "backpacks" from five thrushes and two martins and learn some surprising things.
That some migrants can fly more than 500 kilometres per day, for example, three times quicker than anyone guessed. And that while they tend to take their time on the way south in fall, they positively zip back in spring. One martin took 43 days to reach Brazil, where it spent the winter, and just 13 days to get back! Overall, migration journeys were two to six times faster in spring than it fall, attesting to the birds' high motivation.
Other information scientists are documenting is less exciting, sometimes positively grim. Everyone knows most songbird species are declining. We're finding out how drastic the situation has become.
Take the Canada warbler, a beautiful slaty-backed little bird with a dramatic black necklace across its yellow throat. Populations of this once-common wood-warbler have been shrinking 3.2 per cent a year since 1980, enough that last April the Committee on the Status of Endangered Wildlife in Canada listed the species "threatened."
Contributing factors: 95 per cent of the high Andean forests in Colombia, where the bulk of Canada warblers winter, has been cleared to grow coffee and cacao. Great swaths of Canada's boreal forest, where most nest, are logged each year to feed pulp mills making glossy catalog paper and bathroom tissue. And strike three: vital patches of forest along migration routes, where they rest, are being fragmented.
If you love songbirds, buy shade-grown coffee and chocolate, toilet paper made from recycled fibres and protect your local woodlands!
Nature queries: 905-725-2116 or
mcarney@interlinks.net.
Durham resident Margaret Carney, in addition to writing nature appreciation columns, has also published several children's books.
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