Mongabay: Nearly 60 percent of the 305 species found in North America in winter have shifted their ranges northward by an average of 35 miles, according to an assessment by the Audubon Society. The findings are based on 40 years of data from the group’s Christmas Bird Count — an effort that enlists citizens in a massive bird census each year — and suggest “that global warming is having a serious impact on natural systems.” Over the past 40 years the average January temperature in the United …