492 ORNITHOLOGICAL SKETCHES 
Brehm of Madrid, in 1860, who laid down the following 
characters :— 
I. The white extended further in the region of the shoulder 
than in the Imperial Eagle, so that the broad white band 
reaches along the humeral and cubital parts of the wing 
including the digital. 
II. The general colour of the plumage is darker. 
III. In the young bird, on the contrary, the feathers of the 
underparts are less distinctly striped. 
Besides the eagle which is distinguished by these charac- 
teristics, and which we will for the sake of brevity call 
Adalbert’s Eagle, the true Aguila imperialis also appears 
to exist in Spain, for there I have seen eagles in collections 
which I should without any hesitation have called Imperial 
Eagles, and which, in point of fact, did not differ from the 
Imperial Eagles of our own country in the slightest degree. 
It must, however, be very rare in Spain, for during my 
numerous expeditions into the interior of the country I did 
not see one of these birds. 
As regards this so-called Adalbert’s Eagle, I am by no 
means sure that the species can be retained. Hvery one 
who has been much engaged in the study of the raptorial 
birds, and especially of the eagles, knows that the members 
of that group vary in plumage according to climate and 
habits of life, and to show that one speaks of many forms 
of each species, it is only necessary to cite the cases of the 
“ Stein”? Eagle and the Common Buzzard ; nor is this all, 
for even individual examples of these forms exhibit marked 
differences in size and plumage. Greater caution must 
therefore be exercised in making new species of the raptorial 
than of any other group of birds. 
The dark Aquila adalberti is, in my opinion, Aguila im- 
perialis a little deeper in colour and with a somewhat larger 
