Associated Press: When it comes to global warming, the canary in the coal mine isn’t a canary at all. It’s a purple finch. As the temperature across the continent has become warmer, the purple finch has been spending its winters more than 640 kilometres farther north than it used to. And it’s not alone. An Audubon Society study to be released Tuesday found that more than half of 305 birds species in North America, a hodgepodge that includes robins, gulls, chickadees and owls, are spending the …