CIRCUS SWAINSONII, 



food consists of small quadrupeds, birds, reptiles, &.c. and upon some one or other of these it is 

 often to be seen pouncing in the course of its flight. Damp and marshy situations appear 

 to form its favourite hunting grounds, but it does not, like some of the other Cape species, 

 select those to the exclusion of dry and grassy plains. 



Although I am not possessed of the information which would enable me to state positively 

 the age at which Circxts Swainsonii attains its mature plumage, yet I have reason to believe it 

 appears with the moult of the second year. A female of the first year is represented in Plate 

 XLIV; and fig. 2 of Plate XLIII is a male probably in its second year, just before the adult 

 garb had been fully acquired. The plumage of the young ditl'ers not only in colour, but in 

 various other respects from that of the adult. The feathers in the former, besides being more 

 numerous, better formed, and of a more compact texture, are shorter, broader, and more 

 pointed tiian in the latter. 



This is not the only bird of prey, in which we have observed the texture and form of the 

 feathers to vary with age. In many of the Accipitres of South Africa, like changes occur ; and 

 we find those who have the feathers long, narrow, and pointed in youth, have them short, and 

 with rounded or semicircular points, in mature age — and vice versa, though not in the same re- 

 markable degree. Thus diagnostic characters, drawn from the configuration of feathers, will 

 not prove universally applicable ; indeed, in several instances in which attempts have been 

 made to render the form of these available in the determination of species, confusion and error 

 have been tiie result. The long and pointed feathers of Ze Chass-fiente, Levaillant, have been 

 advanced by some authors as the best and readiest characters, by which it was to be distin- 

 guished from Vulhir fulvus, Lin., of which it is only the young. Having examined hundreds 

 of specimens of the vulture in question, I invariably found all individuals with sallow-coloured 

 plumage — a mark of youth — to have the feathers narrow and pointed, even in the collaret ; 

 while in those with a pale-coloured plumage — -one of the indications of maturity — they were 

 broad and semicircular at the points ; while the collaret consisted of coarse, wiry, or decom- 

 posed feathers, which, in appearance, almost resembled a ruff of slender bristles. I often met 

 with specimens, also, in the intermediate stages between these extremes ; and in many I ob- 

 served feathers of both descriptions upon the same individuals. In the three vultures which 

 occur in South Africa {V.fulviis, Lin., V. auriailaris, Daud., and V. occipitalis, Burchell,) 

 one law seems to prevail ; the feathers, in tlie young of all, are long, narrow, and pointed ; — in 

 the adults, they are short, broad, and rounded, or semicircular at the points. 



Facts, such as these, testify what caution is required, in order to estimate correctly the value 

 of characters, as they appear in individual specimens, which may be presented for examination. 

 Nothing short of a total revision of the characters, both of groups and species, will tend in the 

 slightest degree to free our science from the anomalies, perplexities, and contradictions 

 by which it is at present swallowed up. Such an inquiry, if cautiously and patiently carried 

 through, would supply eitlier what is required, or prove that such a regularity as would enable 

 the naturalist to detect fixed and general laws, does not exist in nature ; or at least is not to 

 be discovered by the cultivators of Natural History of the present day. If the revision 

 be attempted, the degrees of development of individual parts or organs ought especially 

 to be minutely examined, with a view to discover how far such may be available to classifica- 

 tion. At present, we find the degree of development of some one external organ, often consi- 

 dered sufficient to constitute a distinct species, though all other characters of the specimen 

 may be strictly in keeping with those of a species, long known to science. My experience, 



