252 DwiGHT, Phimage-Cycles. \!l% 



of moult. The first annual (a simple or compound juveno-annual) 

 plumage is retained until the first postnuptial moult, but the non- 

 nuptial may be either obliterated by a complete prenuptial moult 

 or more frequently further compounded by the new feathers of a 

 partial renewal. The first non-nuptial therefore is succeeded by a 

 simple first nuptial (juveno-nuptial) as seems to be the case with 

 the Sterninae, the Bobolink {Do/ichouyx oryzii'orus) and other 

 Passeres, or a compound first nuptial as seen in many widely 

 differing species like the Lapla;nd Longspur ( Calcarius lappoiii- 

 cus), Bonaparte's Gull {Lanis pJiilaiklphia) or Ruddy Duck 

 {Erismatura jamaicensis). This last plumage is perhaps the 

 commonest of the ' immature ' plumages, and they are not difficult 

 to understand if we learn their origin. Fortunately for the 

 student most of them are replaced, not later than the first post- 

 nuptial moult by the adult or very nearly adult plumage. Some 

 of the larger Longipennes, Anatidce and others pass a second 

 year in an * immature ' plumage wholly new at the first post- 

 nuptial moult, but their relative numbers are so small that in 

 some species it is possible they represent birds of deficient vitality, 

 a portion at least seeming to assume adult dress, at a consider- 

 ably earlier period than is generally supposed. 



Much of what I have written will, no doubt, seem obscure and 

 complicated, for the facts about plumages and moults do not 

 readily lend themselves to simple explanation, but in summing up 

 the following systematic arrangement of plumages and moults may 

 perhaps help to make the whole subject clearer. 



Derivation of Plu.aiages. 



Natal. Natal. 



Postnatal moult, complete. 

 Juvenal. Juvenal. 



Postjuvenal moult, if complete. 



Annual (simple). ist Annual or simple juveno- 



annual. 



Non-nuptial (simple). ist Non-nuptial or simple ju- 



veno-non-nuptial. 



Postjiwenal moult, if partial. 



Annual (compound). ist Annual or compound juveno- 



annual. 



