美国科学60秒 SSS 2013-08-14（在线收听）

 　　Two centuries ago, blackbirds typically lived out their lives in forrest habitats. Today the birds are one of the most common avian urban species. Researchers have shown that urban and rural blackbirds already differ from one another in their songs, the timing of reproduction, and their risk of diseases. But could the country blackbird and its city cousin now have different personalities? Scientists in Germany collected and hand-raised 28 urban birds and 25 from the country nearby. The researchers tested the birds to determine whether they approached or avoided new objects in a familiar enviornment. They performed the study three times over a year to see if the traits persisted. The urban birds avoided new objects near their feeders for significantly longer than did their rural relatives. The study appears in the journal Global Change Biology. The researchers say these personality differences may be related to genetic microevolutionary changes. And the finding demonstrated two things. One is that urban and rural differences can be tested in a controlled experiment. The second is that blackbirds and many other species may be quickly evolving new behaviors in response to our rapidly urbanizing world.