"The birds who are Citizens are usually the first to build," answered the Doctor. "They merely roved about during the winter months, and had no long journey to make before they reached the home trees again, and then the hardy seed-eating birds can return from the South much earlier than their frailer kin." "Last year," said Rap, "when the men were chopping trees in the great wood beyond the lake, the miller went up one day to hunt coons and took me with him. It was the beginning of March and terribly cold; there were long icicles hanging on the trees, and we were glad enough to go in by the fire in the lumbermen's camp. But what do you think?--if there wasn't an Owl's nest, up in a pine tree, with two eggs in it! It was in a very lonely place, and the miller said the Owl had borrowed an old Crow's nest and fixed it up a little." "I should think the eggs would have frozen hard and been spoiled," said Nat. "No, the old Owl sat on them ever so tight and would hardly budge to let the miller see them. We didn't stay long, for the Owl was a savage big thing, nearly two feet high, with yellow eyes and long feathers sticking up on its head like horns." "A Great Horned Owl," said the Doctor. "I only wonder that it let the miller go near it at all; they are generally very wild and fierce." "This one was sort of friends with the lumbermen," continued Rap, "for they used to hang lumps of raw meat on the bushes for it, and they said it kept the rats and mice away from the camp and was good company for them. It frightened me when I heard it first; it gave an awful scream, like a hurt person. After a while another one began to bark like a dog with a cold, just like this--'who-o-o-o--hoo--hoo--hoo.' And, Doctor, one of the lumbermen told me that with Owls and Hawks the female is mostly bigger than the male. Do you think that is so? Because with singing birds the male is the largest." "Among cannibal birds the female is usually the largest," answered the Doctor, who was pleased to see that Rap so often had a "because" for his questions. "These birds do a great deal of fighting, both in catching their living prey and holding their own against enemies; and as the female stays most at home, being the chief protector of the nest, she needs more strength."