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Smithsonian Scientists Reveal Large-scale Declines in U.S. Bird Populations

Scientists at the Smithsonian Migratory Bird Center in Washington, D.C., and from Wildlife Trust in New York City have found large-scale declines in a diverse array of common North American bird species and say that it warrants immediate attention.

In a study analyzing Breeding Bird Survey data from across North America and spanning the past 26 years, Smithsonian scientists studied population fluctuations both prior to and after the introduction of West Nile virus and found that several species suffered significant declines following West Nile virus outbreaks. The impacted species include several of the most common and familiar: American robin, American crow, blue jay, Eastern bluebird, house wren, tufted titmouse and black-capped chickadee.

Although it has been known that this introduced invasive pathogen does cause bird mortality it was not until now that scientists were able to demonstrate the large-scale impacts across entire species' populations.

"Our work demonstrates the broad and potentially devastating impacts that an invasive pathogen can have on our native wildlife," said Shannon LaDeau, lead author and Smithsonian postdoctoral fellow. "Some species, like the American crow, showed population declines up to 45 percent regionally. It's also important to emphasize that we have only looked at a small subset of bird species in the United States. Most species, such as birds of prey and many waterbirds, aren't monitored at these scales, so we don't have any way of knowing how or if their populations are declining."

Smithsonian scientist and a co-author on the study Peter Marra emphasized that "with increasing globalization often comes dire consequences for our native wildlife and their dependent ecosystems, including unprecedented movement of invasive pathogens around the world. West Nile virus is one pathogen that the public is familiar with due to its impact on humans in the recent past, but West Nile also serves as a clear example of how many other pathogens, such as highly pathogenic avian influenza, can easily enter and affect our ecosystems."

Marra also suggests that these results emphasize the risks associated with global trade in wildlife. International wildlife trade, both legal and illegal, represents one of the primary ways pathogens move around the world. The United States and other countries in the Western Hemisphere should carefully consider banning future trade in wildlife.

Source: Smithsonian