"Are there any other birds besides Gulls that nest on the island, Uncle Roy?" asked Nat. "Yes, the Terns or Sea Swallows that you have seen about the reef nest there also; and this island, as well as the mainland near by, is a favorite stopping-place for all the shore and water birds in their journeys,--from Sandpipers to great flocks of Sea Ducks." "I should think it would be a long swim for Ducks," said Nat; "it is as much as fifteen miles from shore." "They don't swim--they fly there," said Olaf. "Can Ducks fly?" exclaimed Dodo in amazement. "I'm sure the white Ducks at the Farm can only waddle on the ground, or swim and spatter along the water when Wolf or Quick chases them for fun. And anyway their legs are very stiff and queer and grow very far back, as if their bodies were too heavy and going to fall down front, and they had to hold up their heads very high to keep going." "Our tame Ducks are very fat and lazy, for they have lived in captivity for many generations; yet they could fly very well with a little practice. The Mallard, which is a wild River Duck and a swift enduring flyer, is the one which has been domesticated and for hundreds of years kept as a barnyard Duck." "River Ducks?" questioned Rap; "then are there different kinds of Ducks for rivers and lakes, and for salt water?" "There are indeed many kinds of Ducks," said the Doctor, "all of which have easy marks of identification in the beauty-spot on the wings, and many other points about the plumage, as well as the different shapes of their heads, bills, and feet. Though all Wild Ducks, and Geese too, belong to one general family, they are divided into separate groups like cousins, instead of living in one household like brothers. "Almost all Wild Ducks nest in the northern tier of States, or altogether north of them; the hardier species stay with us as winter visitors, but the others only stop to feed, as they follow the rivers and coasts in their migrations. "There was a beautiful Duck that had a nest last year in a tree up near the logging camp; its feathers were as bright as if they had been painted. That is the Wood Duck--one of the exceptions to the rule that Wild Ducks nest on the ground like tame ones. Another kind, the Black Duck, nests as usual on the ground, on a wooded island not far from the one to which we are sailing." "Will you please tell us why Ducks have such waddling legs?" begged Nat. "Because the best legs to swim with are not the easiest to walk with." At that moment the wind died down. The sails flapped once or twice, and then hung loose; and the boat, instead of dashing along, began to drift lazily, with an uncomfortable rolling motion, as the swell, borne in from the ocean many miles away, crept under it. "If the water does that much more, I shall soon be hungry," said Dodo, looking a trifle sad and pressing her hands together over her waist.