EAGLES. 279 



and shorter than those of the hawks ; tarsus evidently shorter than the tibia, usually 

 scutellate in front and behind, or else feathered ; claws always long, much curved and 

 sharp ; wings various, but usually rather short, broad, and rounded. In the progress 

 from youth to maturity the changes in plumage are generally several, and frequently 

 the successive stages are very unlike each other. In other cases, although the young 

 plumage is very unlike that of the adult, the latter is assumed very gradually and 

 almost imperceptibly. In very many cases marked changes of general color resulting 

 from the change in color of the feathers themselves without the loss of any old, or the 

 gain of any new ones. The time required to obtain the adult dress is also very different 

 in different species, and probably varies considerably in individuals of the same species. 

 In not a few the young birds molt at once into the mature dress, in others this is 

 not obtained for at least five or six years, and there seems to be no doubt that occa- 

 sionally there are individuals which never assume it, though they may live to old age. 

 Moreover the various stages peculiar to any given species are not necessarily passed 

 through by every individual, and even if they are, all do not assume them in the same 

 order. Finally, melanism is of frequent occurrence, not only black individuals occa- 

 sionally appearing in almost every species, but black races are not infrequent, in which 

 case the melanism may be (?) only temporary, or, as seems more often to be the case, 

 the abnormal coloration is permanent. Much of what has been said here with regard 

 to variation of plumage is applicable equally to other sub-families, but as it is particu- 

 larly noticeable among the buzzards and eagles I have dwelt on it here. 



In the light of all these facts it will readily be seen how difficult is the discrimina- 

 tion of species, and how perplexing the literature of the subject through the descrip- 

 tion as valid species of all the different forms which a single one may show. As an 

 extreme illustration of the ease with which species are manufactured we may men- 

 tion that in 1875 a European ornithologist of some prominence described as "new" a 

 species, the only example of which was then living in the Zoological Gardens at Ant- 

 werp. This, according to his own description, was extremely similar to a well-known 

 and variable species, and moreover he had actually never seen the bird he described 

 as new. We can therefore hardly be surprised when he mentions as one of the char- 

 acteristics of his new species that it is " silent in confinement." 



Too much reliance has often been placed on the change or permanency of plumage 

 in captive birds ; and while such specimens are frequently invaluable, and we are in- 

 debted to them for much of our true knowledge of change in plumage, yet we should 

 never lose sight of the fact that birds living under abnormal conditions are very liable 

 to become abnormal themselves. 



The age which birds of prey attain is very uncertain, and the data on this point 

 very meagi-e. The general statement has always been that " eagles probably live to 

 be at least one hundred years old." Many cases, indeed, are on record where eagles 

 are believed to have lived more than one hundred years, but we know of no instance 

 where this was absolutely known to be true. At least one authentic instance has been 

 recorded, however, of a white-tailed eagle, Halicetus albicilla, which lived in confine- 

 ment until upwards of eighty years old. 



The eagle-vulture, Gypohierax angolensis, of West Africa, combines, as its name 

 suggests, some characters of both the eagles and vultures. Its size and general bear- 

 ing would place it with the former, but its carrion-eating habits, coupled with the bare 

 skin of the sides of the head, suggest the vultures. It is a beautiful bird in its appear- 

 ance, especially when seen seated solitary, as its custom is, on the bare top of some 



