大学英语六级听力 013（在线收听）

pigeons

There are thousands of pigeons in any big city in the world. But did you know that this common bird is able to find its way home from even a hundreds of kilometers away? Just how pigeons find their way home is a bit of mystery. Some people think that they use landmarks. That is the pigeon knows what the land is like from the air and it uses this like a map. A landmark in Sydeny for example, is the Opera House, which can easily be seen from a long way off. Other possibilities are that pigeons use the position of the sun to work out directions or that they have some kind of built in compass. For quite a few years now, scientists have been caring out experiements on homing pigeons, but they still aren't sure how pigeons find their way home. It seems likely, however, that pigeons like airline pilots use a number of different message to guide them on their long distance journeys. Perhaps, one day we'll learn their secret.