The scale of loss portrayed in the Science study is unlike anything recorded in modern natural history. While the Passenger Pigeon likewise suffered cascading losses more than a century ago, that was a population loss among one species, mostly in eastern North America. This research portrays massive losses among hundreds of species of birds from coast to coast.

The population models in this study are based on several decades of standardized bird-survey datasets. This research represents the most robust synthesis of long-term population monitoring data ever assembled for animals, says Adam Smith, a study coauthor and biostatistician for Environment and Climate Change Canada.

“It’s safe to say that in the natural world, birds are the best studied group of wildlife species,” Smith said. “The data that exist for birds are just so incredible, from 50 years of the North American Breeding Bird Survey and the Christmas Bird Counters from 100 years ago, on to the eBirders of today.