Since Darwin's time, most scientists and school children have assumed that the singing of song birds in the spring is an almost exclusively male trait. But new research by Kevin Omland and Karan Odom of the University of Maryland Baltimore County and colleagues shows that both female and males sing in 71 percent of the surveyed song bird species around the world.
Charles Darwin and other researchers may have been wrong about the singing of female birds in part because of researcher bias. They were men, and fixated on the behavior of male birds. But the scientists may also have been misled by geographical bias. Past researchers were mostly from England and North America, where most songbirds that sing are -- in fact -- males. But this is not true in the tropics and on other continents, where there are many more species of song birds, and female songbirds often sing.