GROWTH AND DEVELOPMENT 89 



Eight Weeks 



Among the adult primaries in addition to number 10 and 9, 8 is now fully developed. 

 Numbers 7, 6 and 5 continue their growth. Growth is complete in juvenile secondaries 

 from number 9 to 15 and the adult feathers from number 1 to 8 are developing^ numbers 

 1 and 8 being still in the pin stage. 



The back and rump are completely covered with pinfeathers of the adult plumage. In 

 practically all cases the juvenile feathers are appended to the tips of the sheaths. This ar- 

 rangement causes the old juvenile feathers to be lengthened and thereby protects the new 

 feathers coming in under them. 



The natal down which is still present in areas previously described is being forced out by 

 adult pinfeathers. In these cases the intermediate or juvenile plumage is omitted. The downy 

 tuft is appended to the tip of the aduh pinfeather. 



Nine Weeks 



Juvenile primary number 4 has been dropped and is being replaced by the adult primary. 

 In like manner numbers 9 and 10 in the juvenile secondaries have been dropped and are 

 being replaced by adult feathers. 



The adult bod) i>lumage continues its growth at approximately the same rate as the juve- 

 nile developed previously. The general pattern fallowed closely |)arallels the succession of 

 feathering from the third to the eighth week. 



Ten Weeks 



Growth of the adult flight feathers continues with only the number 11 juvenile second- 

 ary being replaced by the adult feather. The growth of the number () adult primary has 

 been completed. Numbers 1 and 2 [)rimaries have nearly completed lluir development. 



Juvenile tail feathers drop out between the ninth aii<l Iciilh we.k and are replaced almost 

 inimediateh b) pinfcalhers of the adult iihmiage. 



Eleven Weeks 



From the tenth week to maturity, there is little of significance in the pattern of feather- 

 ing to identify age other than the flight feathers. Therefore, onl\ the development of the lat- 

 ter is discussed. The growth of the aduh flight feathers is complete in numbers 10 to 5 in the 

 primaries and numbers 1 to 6 in the secondaries. Coincident with this, the development is 

 completed in primaries numbers 1 and 2 which, as pointed out previously, are the first feath- 

 ers to appear subsequent to hatching. The juvenile number 3 primary is dropped and is be- 

 ing replaced hv the adult feather. 



Twelve Weeks 



All adult |)rimaries have completed their growth except numbers 3 and 4, while the aduh 

 secondaries from numbers 9 to 13 are developing. 



Thirteen Weeks 



Growth is completed in the fourth adult primary and the tenth adult secondary in addition 

 to those mentioned under the previous week. 



