You can watch them sometimes passing by day so high in the sky that they seem like dust-motes--then perhaps you will only hear a faint call-note and see nothing.

At night the sound of many voices falls from the clouds.

Sometimes it will be the tinkling bell of Bobolinks, sometimes the feeble peep of Snipes, and sometimes the hoarse honk of Wild Geese." "Why, Uncle Roy! Can you tell a bird's name without seeing it, only by one little cry ?" "Yes, my lad.

When you have lived with birds as long as I have, you will know their different voices as you do those of your own family.

When some one calls you in the garden, can't you tell whether it is Dodo or Olive ?" "Yes, but their voices are so _very_ different." "So are the voices of birds, when you know them well." "But the young birds who have been hatched up here--how do they know about going the first time ?" asked Rap.
"The young ones are led in their journeys with signals and cries by their parents; they in turn lead their own young, and so the knowledge is kept up endlessly." "I can see why they go south," said Rap, after thinking a few moments, "but why do they come back again?
Why don't they stay and build their nests down there ?" "That is a difficult question to answer," said the Doctor, "and one that we House People try to explain in different ways.