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 BIRDS' NESTS. 67 treeless regions, and by birds who substitute strings, cotton, or rags for their usual nesting materials. Third, condition of the young at birth, whether feathered or naked. The young of what are termed '• prsecocial " birds are hatched with a covering of downy feathers. Gulls, Ducks, Snipe, Chickens, Par- ^tridges, and Quails are familiar members of this group. Their young can run about soon after birth, and a well- formed nest is not needed. But the young of " altricial " birds are hatched practically naked and are reared in the nest, which is therefore not only a receptacle for the eggs during incubation, but a home. Thrushes, Sparrows, in fact all Perching Birds, Woodpeckers, Hummingbirds, and many others belong in this group of altricial birds. Fourth, temperament, whether solitary or social. Hawks, fierce and gloomy, nest alone, while the cheery, happy Swallows nest in colonies. Fifth, structure of the bird. The tools — that is, the bills and feet — of some birds are more serviceable than those of others. We should not expect a Dove to build the woven nest of an Oriole, nor a Hummingbird to fashion a Woodpecker's dwelling. Sixth, feeding habit. In some few cases feeding habit may determine the character of the nest. For instance. Woodpeckers, in securing their food from trees, often make large excavations, which it is quite natural they should have learned to use as nests. Seventh, inherited habit, or instinct. There seems no reason to doubt that birds inherit their knowledge of nest- building, for in several cases where birds have been taken from the nest and reared alone, they have afterward constructed a nest resembling that of their species. It would therefore appear that inherited habit is a fact. Through it we may explain not only the similarity in the nests of the same species, but also certain habits for