574 



ON SOME SPECIE^ OF THIS 



^ young of the two species that there is a difficulty 

 in discriminating. 



On what ground, therefore, can a strongly mark- 

 ed and constant difference in the plumage of two 

 birds, be accounted for, but on the supposition of 

 their being distinct, particularly when that diffe- 

 rence, instead of gradually disappearing as they 

 approach maturity, and which, if it were the re- 

 sult of immaturity, it must necessarily do, becomes 

 every day the more obvious and defined ? 



An examination of the fine specimen of the 

 full-fledged Ring-tailed Eagle, now exhibited, will 

 carry conviction, that it is not in the plumage of 

 immaturity 



* I find in Cuvier's late work on Natural History, that he 

 does not credit the supposition of the two species above describ- 

 ed being the same. 



I may here state the opinion of that ilhistrious observer con- 

 ' cerning the F. albicilla and F. ossifi-agus, from which it would 

 appear, that these birds, though long described under different 

 names, are not really distinct. His words are : " Ne forment 

 qu'une espese qui, dans ses premieres annees, a le bee noir, la 

 queue noirtare, tachetee de blanchatre, et le plumage brunatre, 

 avec une flamme brun-fonce sur le milieu de la plume (enl. 112. 

 et 415.) et qui, avec Tage, devient d'un gris-brun uniforme, 

 plus pale a la tete et au cou, avec une queue toute blanche et nn 

 bee jaune-pale, (Frisch, 70. t)" 



f •« On a verifie plus d'une fois ce changement a la menagerie du Mu- 

 seum." He further observes in the same note : 



** Quant Siu ^etit pygargue, F, alMccmdus, ce n*est qpue le male du grand 

 P. albiciUa,'' 



