"Some singing birds are real plucky too," said Rap. "That same year I found a Robin's nest in April, when the water-pail by the well froze every night, and a Woodcock's nest in the brushwood. It's hard to see a Woodcock on the nest, they look so like dead leaves. It snowed a little that afternoon, and the poor bird's back was all white, but there she sat. It made me feel so sorry, and I was so afraid she might freeze, that I made a little roof over her of hemlock branches. And she liked that and didn't move at all; so then I wiped the snow off her back, and she seemed real comfortable. I used to go back every day after that to see her; we grew to be quite friends before the four eggs hatched, and I've seen them do queer little tricks; but I never told anybody where she lived, though, because lots of people don't seem to understand anything about birds but shooting or teasing them." "Some day you shall tell us about what the Woodcock did, my lad. You must tell us a great many stories, for you know what you have seen yourself. That is the best knowledge of all, and it will encourage Nat to hear you," and Dr. Hunter put his arm affectionately around the shoulders of each boy. "Hush! Wait a moment and listen to that Thrasher," said the Doctor, stopping behind some thick bushes; "he is wooing his mate!" "What is wooing?" whispered Nat. "Asking her to marry him and come and build a cosy home in one of these nice bushes. Listen! See! There he is, up on the very top of that young birch, with his head thrown back, singing as if his throat would split." As the children looked up they saw a fine bird with a curved beak, rusty-brown back, and light breast streaked with black, who was clinging to a slender spray, jerking his long tail while he sang. "It seems as if I could almost hear the words he says," said Rap. "Birds sing in many different tones," said the Doctor. "The Thrasher's song is like some one talking cheerfully; the Meadowlark's is flute-like; the Oriole's is more like clarion notes; the Bobolink bubbles over like a babbling brook; while the dear little brown striped Song Sparrow, who is with us in hedge and garden all the year, sings pleasant home-like ballads." "There are some birds that Olive told me can't sing a bit," said Nat, "but only call and squeak. How do they ask their mates to marry them?" "All birds have alarm cries, and a call-note that serves the same purpose as a song, although it may not seem at all musical to us. We are naturally more interested in that order of birds whose voices are the most perfectly developed. These not only sing when they are courting, but all the time their mates are sitting upon the eggs, and until the young are ready to fly." "Why do birds always build nests in spring?" asked Nat. "I think because there is more for them to feed the little ones with, than when it gets to be hot and dry," said Rap, "and it gives them time to grow big and strong before winter comes, when they must go away."