Page:Natural History, Birds.djvu/43

30 up without ever having heard the song of its species, it would be destitute of it.

It is in this Order, also, that we find the instinct of nest-building most perfectly displayed. The specimens of nests which are prepared, we can hardly say built, by other birds, are rude structures, consisting mostly of loose aggregations of rough materials with scarcely an attempt at construction. But very many of the Passerine birds build most elaborate and elegant structures, of which we may mention as instances, the compact felted nests of the Humming-bird, of the Gold-finch, and of the Bottle-tit, and the woven purses of the Orioles and the Starlings.

The study of this immense assemblage of species is facilitated by its sub-division into four Tribes, characterized by the varying form of the beak, and named respectively Fissirostres, Tenuirostres, Dentirostres, and Conirostres.

The beak in this Tribe is short, but broad, and more or less flattened horizontally, often hooked at the tip, with the mouth very deeply cleft: the upper mandible is not notched. The feet are small and feeble. Most of the species feed on insects, which they capture on the wing, but one genus subsists on fishes.

The tropical regions are the principal home of the fissirostral birds; such species as reach to the temperate zone, are, for the most part, migratory