Populations of rare and common birds alike are decreasing across North America, including (clockwise from top left) snowy owls, sanderlings, cactus wrens and Western meadowlarks.
Nearly 3 billion fewer birds exist in North America today than in 1970.
While scientists have known for decades that certain kinds of birds have struggled as humans (and bird-gobbling cats) encroach on their habitats, a new comprehensive tally shows the staggering extent of the loss. Nearly 1 in 3 birds — or 29 percent — has vanished in the last half century, researchers report September 19 in Science.
"Three billion is a punch in the gut," says Peter Marra, a conservation biologist at Georgetown University in Washington, D.C. The loss is widespread, he says, affecting rare and common birds alike. "Our study is a wake-up call. We're experiencing an ecological crisis."
Comment: Some recent reports demonstrating the increasingly aggressive behavior shown by bears which have resulted in serious injuries and even fatalities: