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The West Nile virus is taking a toll on the native bird population within the United States, a new study found.

For this study, the research team headed by Ryan Harrigan of the University of California, Los Angeles set out to examine the effects of the virus, which can be transmitted via infected mosquitoes, on 49 species of wild birds. The team collected data at more than 500 bird banding locations throughout the U.S. between 1992 and 2007.

Harrigan and his colleagues reported that the West Nile virus was linked to the declining survival rates in 23 of the 49 bird species studied. 11 out of the 23 species experienced a decline in their survival rates once the virus arrived in their environment. These species, which included the field sparrow and the downy woodpecker, were able to recover to the levels that they were at prior to the virus.

The remaining 12 species, which included the purple finch and the Swainson's thrush, were not able to get their population levels back up.

"The declines in annual survival documented here are substantial and may have lasting effects on population abundances and growth rates of affected species," the authors wrote.

They continued, "Although the causes of these patterns are not fully understood, similarities between the impacts of disease on closely related species could be the result of common immunological responses across sister taxa, shared physiological and metabolic functions in closely allied species, or common diets and behavior among clades [groups of birds that evolved from a common ancestor. It is also possible that these characteristics are associated with common high-risk habitats for West Nile Virus in closely related species."

The West Nile virus was first found in the U.S. in 1999. Since then, research has been mostly focused on how the virus affects humans.

The study was published in the Proceedings of the National Academy of Sciences.