National Geographic: Climate change could threaten half of North American birds by the end of the century, according to a new study from the National Audubon Society. Half of the birds of North America are at risk of extinction, says Gary Langham, Audubons chief scientist. That estimate is based on the 314 bird species, out of 588 studied, that could lose most of the area they currently occupy, because of a warming planet. Nearly 200 of these threatened species may find hospitable conditions elsewhere, but for 126...