252 The Naturalst 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 hfe which makes solitude necessary. Thus, a 
large proportion of species are found to pair for 
