NASHVILLE — During the nearly quarter-century that my family has lived in this house, the changes in our neighborhood have become increasingly apparent: fewer trees and wildflowers, fewer bees and butterflies and grasshoppers, fewer tree frogs and songbirds. The vast majority of Tennessee is still rural, and for years I told myself that such changes were merely circumstantial, specific to a city undergoing rapid gentrification and explosive growth. I wasn’t trying to save the world by putting up nest boxes for the birds or letting the wildflowers in my yard bloom out before mowing. I was hoping only to provide a small way station for migrating wildlife, trusting they would be fine once they cleared the affluence zone that is the New Nashville.

I was wrong. A new study in the journal Science reports that nearly 3 billion North American birds have disappeared since 1970. That’s 29 percent of all birds on this continent. The data are both incontrovertible and shocking. “We were stunned by the result,” Cornell University’s Kenneth V. Rosenberg, the study’s lead author, told The Times.

This is not a report that projects future losses on the basis of current trends. It is not an update on the state of rare birds already in trouble. This study enumerates actual losses of familiar species — ordinary backyard birds like sparrows and swifts, swallows and blue jays. The anecdotal evidence from my own yard, it turns out, is everywhere.

You may have heard of the proverbial canary in the coal mine — caged birds whose sensitivity to lethal gasses served as an early-warning system to coal miners; if the canary died, they knew it was time to flee. This is what ornithologists John W. Fitzpatrick and Peter P. Marra meant when they wrote, in an opinion piece for The Times, that “Birds are indicator species, serving as acutely sensitive barometers of environmental health, and their mass declines signal that the earth’s biological systems are in trouble.”