September 19, 2019 - NPR

North America Has Lost 3 Billion Birds, Scientists Say

Over the past half-century, North America has lost more than a quarter of its entire bird population, or around 3 billion birds.

That's according to a new estimate published in the journal Science by researchers who brought together a variety of information that has been collected on 529 bird species since 1970."By our estimates, it's a 30% loss in the total number of breeding birds"says Ken Rosenberg, an applied conservation scientist at the Cornell Lab of Ornithology in Ithaca, N.Y.