366 ae MR. J. H. GURNEY ON AQUILA DESMURSII. 
which the feathers have been also newly acquired, and which in this stage bear a con- 
siderable general resemblance in point of colouring to the immature specimens of Aquila 
pennata, though I have never met with an immature Aquila pennata quite so dark as 
some specimens I have seen of Aquila desmursti. In Aquila desmursii, as also in Aquila 
nevioides, both adult and immature birds appear liable to have their plumage exceed- 
ingly bleached by the action of the tropical sun ; but it is remarkable that the feathers 
composing the occipital crest of Aquila desmursit appear to retain their original tint, 
notwithstanding the partial loss of colour from the above cause in the portions of the 
plumage immediately adjacent. It should also be remarked that in some immature 
specimens nearly the whole under surface is of a very pale whitish brown—a variety 
from the ordinary darker colouring which cannot be accounted for by the effect of sun 
and weather only. 
In conclusion, I will add the remarks on this species communicated to me by M. 
Jules Verreaux, which are as follows :—‘‘ According to the notes of the collectors, the 
irides of the adult birds are of a chestnut-brown tinged with yellow ; whilst in the 
young birds the yellow tint is absent, and the brown is deeper, with but little tinge of 
chestnut. The natives (at Bissao) give the name of ‘ Socolas ’ to this species only, it 
being well known to them as a very courageous bird, attacking even the small Gazelles 
(Cephalophorus maawelli) which inhabit the same localities, and also preying on various 
birds, and especially the Francolinus bicalcaratus.” 
The figures in the accompanying plate, by Mr. Wolf (Pl. LXXVII.), represent three 
specimens of Aquila desmursi, from the collection of the Norwich Museum, in the three 
different states of plumage above referred to. 
