It's surprising to see so many comments here jumping to the conclusion that the article is pointing the finger at carbon emissions. It's not. The article doesn't credit any single cause with the drop. Nor does it spin any solutions.

It does note a correlation, and from that a possible cause. And there, the link between observation and putative cause is not supported:

> The hardest hit were grassland birds, down by more than 50 percent, mostly due to the expansion of farms that turn a varied landscape into acres of neat, plowed rows

The article mainly reports a numerical finding.