Dying birds and the fires: scientists work to unravel a great mystery

The yellow Townsend Warbler lay lifeless on the gravel ground near Grant county, New Mexico, the eyes in its yellow-striped head closed, its black feathery underbelly exposed. Just days before, the migrating bird – weighing 10 ounces, or the equivalent of two nickels – might have been as far north as Alaska. But it met an untimely demise in the American south-west, with thousands of miles still to go before reaching Central America, its…