"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 grams, 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 destination for the winter.
The warbler is one of hundreds of thousands of birds that have recently turned up disoriented or dead across the region, where ornithologists have described birds “falling from the sky”.
The mass die-off has been tentatively attributed to the historic wildfires across California, Oregon and Washington in recent months, which may have forced birds to rush their migration. But scientists do not know for sure – in part because nobody knows precisely how wildfire smoke affects birds."