Shrinking North American bird population getting worse faster. Experts blame this

A new study finds North American bird populations keep dropping, and that decline is speeding up for many species

WASHINGTON -- 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.

“Not only are we losing birds, we are losing them faster and faster from year to year,” said study co-author Marta Jarzyna, an ecologist at Ohio State University. “Except for forest birds, almost every group is doing poorly. So we need to ask ourselves a question. How do we protect these groups of birds?”

The only consolation is that the birds that are shrinking in numbers the fastest are species — such as the European starling, American crow, grackle and house sparrow — with large enough populations that they aren't yet at risk of going extinct, said study lead author Francois Leroy, also an Ohio State ecologist.

“The thing is that species extinction, they start with a decline in abundance,” Leroy said, adding that “the decline is somehow maybe giving a preview of what it could lead to in terms of species extinction.”