Though the continent has lost 3 billion birds since 1970, those losses are hard to glean because it’s the commonest species that have been hit hardest.
In the early afternoon of September 1, 1914, Martha the passenger pigeon, the last of her kind in the world, passed away, and her entire species disappeared with her. But before that instant of extinction, there had been decades of decline, as hunters killed what was once the most common bird in the world. Billions of passenger pigeons became millions, thousands, and then hundreds, until eventually one became none. Few people took note of this decline as it happened: There still seemed to be a lot of pigeons, and their abundance obscured their downfall.
History is now repeating itself—across the entire avian world.
A new study, which analyzed decades of data on North American birds, estimates that the continent’s bird populations have fallen by 29 percent since 1970. That’s almost 3 billion fewer individuals than there used to be, five decades ago. “It’s a staggering result,” says Kenneth Rosenberg from Cornell University and the American Bird Conservancy, who led the analysis.