ROUGH-LEGGED FALCON. 219 



southern parts of Europe, any more than to the south of the State of 

 Maryland in North America. 



As connected with this subject, I may here offer a few observations 

 respecting the gradual improvement of the colours of birds, in their 

 progress toward maturity. 



In the Rough-legged Falcon, which forms the subject of this article, 

 I feel convinced that the younger birds will generally be found to be 

 of much lighter tints than the old, and that these tints become, as in 

 all other species^ stronger, piu'er, or firmer, with age. As this may call 

 for an explanation, I will offer it to you. 



The colours of an old bird may be darker or lighter than that of the 

 young of the same species, until the latter has acquired its full plumage ; 

 but in the mean time the differences of which I now speak, will prove 

 apparent between the two birds on the slightest inspection of the ex- 

 perienced student of nature. In birds of which the colouring must 

 ultimately become splendent, the colours of the young are generally of 

 a different character, that is to say considerably duller ; while in spe- 

 cies of which the adult exhibit dull colours, the young are found at first 

 to have their plumage almost similar to that of their parents. Such is 

 the case, for example, in the greater number of our Finches and Thrushes. 

 "Whilst in those of more striking colours when old (that is, when they 

 have obtained their full colouring, whether at the first moult or at suc- 

 ceeding moults) the markings are such as at once suffice to indicate 

 the species to which they belong. 



In the Hawk family I have observed that the younger the indivi- 

 dual is, the lighter are its colours and markings, and that even in those 

 which after a while either lose or gain the bands on the tail, the gene- 

 ral colour of that part becomes purer or more firm, whether barred, or 

 of a uniform hue, as in the case of our Red-tailed Hawk, Falco borealis. 

 The same observation will apply to our Falco Spanerius, and Buteo li- 

 neatus, the bands of the tail of which, like those of Buteo lagopus and 

 B. penmyhanicus, become more purely white and black the more the 

 individual advances in age. 



I have also observed that in all the old birds of certain species which 

 were able to reach the higher latitudes for the purpose of breeding, the 

 mass of their colotu*ing was much superior to that of such birds of the 

 same species as were by circumstances rendered incapable of reaching 

 the same parallel. Thus, all the Finches which I found breeding in 



