A robin nests in a traffic light near 19th and Tennessee streets. A new study of the effects of West Nile virus on bird populations finds that robins have been among the hardest-hit.

Washington ? Birds that once flourished in suburban skies, including robins, bluebirds and crows, have been devastated by West Nile virus, a study found.

Populations of seven species have had dramatic declines across the continent since West Nile emerged in the United States in 1999, according to a first-of-its-kind study. The research, to be published today by the journal Nature, compared 26 years of bird breeding surveys to quantify what had been known anecdotally.

“We’re seeing a serious impact,” said study co-author Marm Kilpatrick, a senior research scientist at the Consortium of Conservation Medicine in New York.

West Nile virus, which is spread by mosquito bites, has infected 23,974 people in confirmed cases since 1999, killing 962, according to the Centers for Disease Control and Prevention.

But the disease, primarily an avian virus, has been far deadlier for birds. The death toll for crows and jays is easily in the hundreds of thousands, based on the number dead bodies found and extrapolated for what wasn’t reported, Kilpatrick said.

It hit the seven species – American crow, blue jay, tufted titmouse, American robin, house wren, chickadee and Eastern bluebird – hard enough to be scientifically significant. Only the blue jay and house wren bounced back, in 2005.

The hardest-hit species has been the American crow. Nationwide, about one-third of crows have been killed by West Nile, said study lead author Shannon LaDeau, a research scientist at the Smithsonian Migratory Bird Center in Washington. The species was on the rise until 1999.

In some places, such as Maryland, crow loss was at 45 percent, and around Baltimore and Washington, 90 percent were gone, LaDeau said.

Researchers noted the die-offs came in patches, with many in some places and none in others. Maryland appeared to be the epicenter of bird deaths.

Chickadees, Eastern bluebirds and robins in Maryland were 68 percent, 52 percent, and 32 percent below expected levels in 2005. Tufted titmouse populations in Illinois were one-third of what they were expected to be.

“It tends to be more suburban areas. Some of the common backyard species including the blue jays, the robins, the chickadees, have suffered significant declines,” LaDeau said. “That heavily packed urban corridor is a bad place to be a bird. The reason for that is that the mosquito prefers human landscape. They do very well in suburbia.”