"I used to call those birds Chimney 'Swallows,' but Olive says they are made more like Hummingbirds and Nighthawks than real Swallows," continued Rap. "Nighthawks?" said Nat. "I thought Olive said Hawks were cannibal birds. How are they relations of Swallows?" "That is a mistake a great many people make," said the Doctor; "for the Nighthawk is not a real Hawk, but a shy bird, who has a rapid hawk-like flight, though it eats nothing but beetles, moths, and other insects. Hark! Do you hear that cry high in the air?" "As if something was saying 'shirk-shirk'?" said Nat. "Yes; that is a Nighthawk on its way home. Look! he is over us now, and you can see two large white spots like holes in his wings. By these you can tell it from any of the real Hawks." "Does he build high up in a tree?" asked Rap. "I have never found his nest." "There is a good reason for that," said the Doctor. "There is no nest. Two eggs are laid on the bare ground, that is about the same color as the bird itself; and the eggs look too much like streaky pebbles to be easily seen. When the young are hatched they keep still until they are able to fly, and are colored so exactly like the place upon which they rest that it is almost impossible to see them, even if you know where they are." "How much there is to learn!" sighed Nat. "I'm afraid you will have to make us a big book instead of a little one, Uncle Roy, to teach us all these things. Olive and Rap have such a start of us. Dodo and I don't know much of anything, and even what I thought I knew about birds isn't very true." "Don't be discouraged, my boy; you do not need a big book--a little one will do for the present. What you need is patience, a pair of keen eyes, and a good memory. With these and a little help from Olive, Rap, and your old uncle, you can learn to know a hundred kinds of every-day birds--those that can be found easily, and have either the sweetest songs, the gayest plumage, or the most interesting habits. Some we shall find here in the lane and swamp meadow, or by the river. Others have made their home in my orchard for years. And I am going to put in the book more than a hundred beautiful pictures for you and Dodo, drawn so naturally that you can tell every one of the birds by them, and that will make it easier for you to understand what you read. "For some of the water birds we must go up to the lake or in the summer make a trip over to the seashore. How do you like that? Yes, you too, Rap. By and by, when you know these hundred birds by name and by sight, you will be so far along on the road into Birdland that you can choose your own way, and branch off right and left on whatever path seems most attractive to you; but then you will need big books, and have to learn long hard Latin names." "What birds will you begin with, please, Doctor Roy," said Rap, "the singers or the cannibals?"