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 Aquila 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. Every 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, Aquila im- 

 perialis a little deeper in colour and with a somewhat larger 



