Billions fewer birds are flying through North American skies than decades ago and their population is shrinking ever faster, mostly due to a combination of intensive agriculture and warming temperatures, a new study found.
Nearly half of the 261 species studied showed big enough losses in numbers to be statistically significant and more than half of those declining are seeing their losses accelerate since 1987, according to Thursday's journal Science. The study is the first to look at more than the total bird population by examining the trends in their decrease, where they are shrinking the most and what the declines are connected to.
