NESTLING BIRDS AND WHAT THEY TEACH 245 



birds, is a curious and extremely interesting point, and not 

 only reveals a change in the tactics adopted for the escape of 

 enemies, but draws attention to another, and what we may 

 regard as a second string to the bow, practised by the Game- 

 birds themselves. It must be remembered then that these 

 latter are reared in comparatively large families, and that they 

 in consequence afford a conspicuous and tempting prey to 

 prowling carnivora. Accordingly, as soon as danger is realised 

 by the parent, the alarm is given and the young scatter in all 

 directions. Halting at last, they then fall back upon this 

 " second string " — protective coloration. That is to say, they 

 have, in addition to the remarkably accelerated flight, also 

 acquired a peculiar type of plumage which enables them to 

 assimilate with the surrounding objects. Now it would seem 

 that this precocious power of flight has not proved a really 

 satisfactory method of escape, inasmuch as in fleeing from 

 immediate danger the young either strayed too far to render 

 recall possible, or they fled into new danger. Consequently, 

 the young in other groups have come to rely either on pro- 

 tective coloration alone, or at most run but a few yards and 

 then squat down. Or, as in the case of one of the Coursers, 

 the parents cover the young with earth. On this account, then, 

 other groups have discarded the doubtful refuge afforded by 

 precocious flight, and with it the evidence of these earlier 

 arboreal habits. The young of aquatic birds obviously do not 

 need to seek safety in flight. Concealment amid reed-beds or 

 other vegetation affords ample protection. Among all these 

 non-flying young we find the development of the quills has 

 been retarded rather than accelerated, so that they appear 

 together with the rest of the body plumage. Among the Ducks, 

 indeed, the quills do not appear till extremely late, so that the 

 body has attained almost its full size before the wing begins to 

 attain its adult form. 



The wing of the nestling Rhea — the South American 

 Ostrich — still retains traces of evidence of a developmental 

 history precisely similar to that of the forms which we have 

 been discussing. Whether such traces will be found in the 

 other flightless members of the Ostrich tribe, remains to be 

 seen. In the Tinamous, the only Ostrich-like birds which 

 have retained the power of flight, the development of the wing 



