96 DWIGHT 



spicuously among the last to be moulted. If the species under- 

 goes a partial prenuptial moult a few throat feathers may be all that 

 are renewed, but usually new growth extends as far as the pec- 

 toral forking. In some species with a more extensive moult at 

 this season, the whole tract, or all of it except its posterior ex- 

 tremity is renewed, and there is much individual variation besides 

 in the amount of renewal. 



6. Caudal or Tail Tract (Pteryla caudalis). From this tract 

 grow the rectrices and their upper and under coverts, and the 

 anal circlet and crissum may conveniently be included for their 

 moult coincides with that of the adjacent coverts. Most of 

 the feathers of this tract are large and not numerous, the twelve 

 rectrices or tail feathers being the most important of them all. 

 Their moult is late and is usually preceded by that of the" upper 

 and under coverts nearest to them. At about the time the sixth 

 or fifth primary is lost the renewal of the rectrices begins but 

 it is irregular especially in young birds. The rectrices fall out 

 approximately in pairs beginning with the central pair, and fol- 

 lowed by the quills next adjacent on either side. The process 

 is so rapid however, that when the outer pair falls, the middle 

 ones are seldom more than half grown and the whole series is 

 usually found in a pulpy condition at a time when the rest of 

 the body plumage is well developed and the first primary nearly 

 or quite grown. The sheaths of these feathers adhere unevenly 

 giving the impression of more irregularity in their moult than 

 really exists, but there are evidently a good many cases where 

 the normal sequence is violated. 



In young birds just from the nest, the wings are often well 

 developed before the tail shows much growth and bob-tailed 

 adults as well as young birds are often seen together at the 

 season of moult. The coverts mostly reach maturity before 

 the tail itself, the rows nearest to its roots tending to precede 

 in their order of moult those at a distance, although there is 

 considerable irregularity. 



The rectrices are regularly renewed whenever all the remiges 

 are moulted, and they are often moulted when the latter are 

 not, especially in young birds which assume much of the adult 



