信鸽送信，怎么认得回家的路？

Homing pigeons can fly home from far away. 信鸽从很远的地方，也能飞回家。 They sense the Earth's magnetic field. 它们能感觉到，地球的磁场。 They also read the position of the Sun. 它们还能看，太阳的位置。 Some even use smells as a map. 有些鸽子，还靠气味认路。 That is how they find home after hundreds of kilometers. 飞出几百公里，也能找回家。 People used them to send letters long ago. 古时候，人们就靠它们送信。