why do swan fly south?

why do swan fly south? 脑筋急转弯 Why do birds fly south? Why do birds fly south for winter Why do you like Sparks Fly? riddle:why do birds fly south for winter why do brids fly south in the winter?是脑筋急转弯的 How.do.people.find.the.white.swan?中文是什么 why does the bird fly Why the bird can fly Riddles:Why do people go to bed?Why do birds fly south?wo de ying yu xue de bu hao= =. 英语翻译1.Why do birds fly to south?2.There is four mistake in this centence.Can you find them? 为什么时光流逝?why does time fly? 脑筋急转弯 Why does time fly? fly boy why读音是否相同 脑筋急转弯Why deos time fly swan是什么意思? swan是什么意思. () did you feel disappointed?用when，what，why，where填空。（）will you fly to New York？（）does he usually do at weekend？