At other hours and seasons the general aspect of the plain is monotonous, and in spite of the unobstructed view, and the unfailing verdure and sunshine, somewhat melancholy, although never sombre: and doubtless the depressed and melancholy feeling the pampa inspires in those who are unfamiliar with it is due in a great measure to the paucity of life, and to the profound silence. The wind, as may well be imagined on that extensive level area, is seldom at rest; there, as in the forest, it is a "bard of many breathings," and the strings it breathes upon give out an endless variety of sorrowful sounds, from the sharp fitful sibilations of the dry wiry grasses on the barren places, to the long mysterious moans that swell and die in the tall polished rushes of the marsh. It is also curious to note that with a few exceptions the resident birds are comparatively very silent, even those belonging to groups which elsewhere are highly loquacious. The reason of this is not far to seek. In woods and thickets, where birds abound most, they are continually losing sight of each other, and are only prevented from scattering by calling often; while the muffling effect on sound of the close foliage, to' which may be added a spirit of emulation where many voices are heard, incites most species, especially those that are social, to exert their voices to the utmost pitch in singing, calling, and screaming. On the open pampas, birds, which are not compelled to live concealed on the surface, can see each other at long distances, and perpetual calling is not needful: moreover, in that still atmosphere sound travels far. As a rule their voices are strangely subdued; nature's silence has infected them, and they have become silent by habit. This is not the case with aquatic species, which are nearly all migrants from noisier regions, and mass themselves in lagoons and marshes, where they are all loquacious together. It is also noteworthy that the subdued bird-voices, some of which are exceedingly sweet and expressive, and the notes of many of the insects and batrachians have a great resemblance, and seem to be in accord with the aeolian tones of the wind in reeds and grasses: a stranger to the pampas, even a naturalist accustomed to a different fauna, will often find it hard to distinguish between bird, frog, and insect voices.