A study released today by the Audubon Society has found that a significant number of North American bird species have changed their migratory patterns over the last 40 years, finding more Northern homes for the winter, likely as a result of increased temperatures over the United States during that time period.
Of the 305 species observed during the Society’s annual Christmas Bird Count over the last four decades, nearly 60% have shifted their winter homes further North, some as far away as 400 miles from their homes of the 1960’s. According to the report, this Northern shift of 177 observed bird species has occurred at the same time average temperatures of the coldest month, January, over the continental United States have increased more than five degrees Fahrenheit.
It is not what each of these individual birds did. It is the wide diversity of birds that suggests it has something to do with temperature, rather than ecology.
– Greg Butcher, study lead scientist and director of bird conservation, Audubon Society
Several species have also shifted away from more temperate coastal areas to previously inhospitable inland abodes.
Figure 1: Migration changes for 20 bird species; Graphics source: AP; Data sources: Audubon Society, NOAA