First and foremost of the Falconidæ are the eagles. Let me preface what little I have to say about these birds with the remark that I am unable to set forth any characteristics whereby a novice may recognise an eagle when he sees one on the wing. The reader should disabuse his mind of the idea he may have obtained from the writings of the poets of the grandeur of the eagle. Eagles may be, and doubtless often are, mistaken for kites. They are simply rather large falcons. They are mostly coloured very like the kite.
All true eagles have the leg feathered to the toe. I give this method of diagnosis for what it is worth, and that is, I fear, not very much, because eagles as a rule do not willingly afford the observer an opportunity of inspecting their tarsi.
The eagles most commonly seen in the Himalayas are the imperial eagle (Aquila helica), the booted eagle (Hieraëtus pennatus), Bonelli's eagle (Hieraëtus fasciatus), the changeable hawk-eagle (Spizaëtus limnaëtus), and Hodgson's hawk-eagle (Spizaëtus nepalensis).
The imperial eagle has perhaps the darkest plumage of all the eagles. This species does not live up to its name. It feeds largely on carrion, and probably never catches anything larger than a rat. The imperial eagle is common about Mussoorie except in the rains. Captain Hutton states that he has seen as many as fifty of them together in the month of October when they reassemble after the monsoon.
The booted eagle has a very shrill call. Its lower parts are pale in hue.
Bonelli's eagle is fairly common both at Naini Tal and Mussoorie. It is a fine bird, and has plenty of courage. It often stoops to fowls and is destructive to game birds. It is of slighter build than the two eagles above described. Its lower parts are white.
The changeable hawk-eagle is also a fine bird. It is very addicted to peafowl. The hillmen call it the Mohrhaita, which, being interpreted, is the peacock-killer. It utters a loud cry, which Thompson renders whee-whick, whee-whick. This call is uttered by the bird both when on the wing and at rest. Another cry of this species has been syllabised toot, toot, toot, toot-twee.
Hodgson's hawk-eagle is also destructive to game. It emits a shrill musical whistle which can sometimes be heard when the bird is so high as to appear a mere speck against the sky. This species has a narrow crest.