The fourth kind of eagle is the “percnopterus,”[2899] also called the “oripelargus;”[2900] it has much the appearance of the vulture, with remarkably small wings, while the rest of the body is larger than the others; but it is of a timid and degenerate nature, so much so, that even a raven can beat it. It is always famishing and ravenous, and has a plaintive murmuring cry. It is the only one among the eagles that will carry off the dead carcase; the others settle on the spot where they have killed their prey. The character of this species causes the fifth one to be known by the distinctive name of “gnesios,”[2901] as being the genuine eagle, and the only one of untainted lineage; it is of moderate size, of rather reddish colour, and rarely to be met with. The haliætus[2902] is the last, and is remarkable for its bright and piercing eye. It poises itself aloft, and the moment it catches sight of a fish in the sea below, pounces headlong upon it, and cleaving the water with its breast, carries off its prey. The eagle which we have mentioned as forming the third species, pursues the aquatic birds in the vicinity of standing waters: in order to make their escape they plunge into the water every now and then, until at length they are overtaken by lassitude and sleep, upon which the eagle immediately seizes them. The contest that takes place is really a sight worthy to be seen. The bird makes for the shore to seek a refuge, and especially if there should happen to be a bed of reeds there; while in the meantime the eagle endeavours to drive it away with repeated blows of its wings, and tumbles into the water in its attempts to seize it. While it is standing on the shore its shadow is seen by the bird, which immediately dives beneath, and then making its way in an opposite direction, emerges at some point at which it thinks it is the least likely to be looked for. This is the reason why these birds swim in flocks, for when in large numbers they are in no danger from the enemy; as by dashing up the spray with their wings they blind him. Again, it often happens that the eagle is not able to carry the bird aloft on account of its weight, and in consequence they both of them sink together. The haliætus, and this one only, beats its young ones while in an unfledged state, with its wings, and forces[2903] them from time to time to look steadily upon the rays of the sun; and if it sees either of them wink, or even its eye water, it throws it headlong out of the nest, as being spurious and degenerate, while, on the other hand, it rears the one whose gaze remains fixed and steady. The haliætus[2904] is not a species of itself, but is an eagle of mixed breed: hence their produce are of the species known as the ossifrage, from which again is produced the smaller vulture; while this in its turn produces the large vulture, which, however, is quite barren.