The Desert Pampas. 9 



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, especi- 

 ally 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 need- 

 ful : 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 ssolian 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. 



The mammalia is poor in species, and with the 

 single exception of the well-known vizcacha 

 (Lagostomus trichodactylus), there is not one of 



