252 The Naturalist in La Plata. 



big, strong-domed nest or deep burrow, all the eggs 

 are hatched and all the young reared, the thinning- 

 out process commencing only after the brood has 

 been led forth into a world beset with perils. With 

 other families, on the contrary, the greatest amount 

 of destruction falls on the eggs or fledglings. I 

 have frequently kept a dozen or twenty pairs of 

 different species warblers, finches, tyrants, star- 

 lings, &c. under observation during the breeding 

 season, and have found that in some cases no young 

 were reared at all ; in other cases one or two young ; 

 while, as often as not, the young actually reared 

 were only parasitical starlings after all. 



I have still to speak of the voice of the tree- 

 creepers, an important point in the study of these 

 birds ; for, though not accounted singers, some 

 species emit remarkable sounds ; moreover, language 

 in birds is closely related to the social instinct. 

 They seem to be rather solitary than gregarious ; 

 and this seems only natural in birds so timid, weak- 

 winged, and hard pressed. It would also be natural 

 to conclude from what has been said concerning 

 their habits that they are comparatively silent ; for, 

 as a rule, vigorous social birds are loquacious and 

 loud-voiced, while shy solitary kinds preserve 

 silence, except in the love season. Nevertheless 

 the creepers are loquacious and have loud resonant 

 voices ; this fact, however, does not really contra- 

 dict a well-known principle, for the birds possess 

 the social disposition in an eminent degree, only the 

 social habit is kept down in them by the conditions 

 of a life which makes solitude necessary. Thus, a 

 large proportion of species are found to pair for 



