The more birds flying around, the lower the chance that the West Nile virus is hitching a ride.
Researchers at Washington University have discovered that the odds of humans catching the virus go down when the bird population in an area is more diverse, or there are lots of bird species.
Some bird species are more attractive to mosquitoes, which can feed on the blood of infected birds and pass the virus along when they bite humans.
Robins are the most common carriers of the virus since they eat primarily off the ground, exposing them to the low-flying bugs. Crows, blue jays, sparrows and house finches are also prime candidates for the virus.
But most bird species aren't typical carriers of West Nile and are less likely to transfer the virus to mosquitoes. So when birds are more diverse and evenly distributed, fewer of them are likely to be disease carriers.
The researchers looked at bird surveys in the St. Louis area and nationwide and compared the data to infected mosquito numbers in the regions. Like most urban areas, St. Louis' bird population gets more colorful the farther you get from the city.
"In St. Louis city you'll tend to see relatively low bird diversity," said Brian Allan, one of the researchers and a doctoral candidate in biology at Washington University. "As you get out into suburban and rural parts of the St. Louis metropolitan area, you see some pretty healthy bird diversity."
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