Members of the genus Ictinaetus are large, but lightly built eagles with small beaks. They have very long wings and a long tail. The legs are feathered, and the talons long, but only slightly curved. The outer digit is quite short. These characteristics of the feet are probably adaptations for taking nestling birds from tree-top nests. There is a slight crest, formed by the pointed feathers of the crown. The adult is mostly black; the immature more buff.
This genus is probably a specialised booted eagle, but there is some evidence, that it is closely related to the kites, although that would make the feathered tarsi difficult to explain. The genus contains one species in tropical Asia.
Immatures are dark sepia brown above, the feathers of crown and nape and some on the back are tipped with buff. The upper tail coverts are banded with sepia and buff making a pale bar across the base of the tail. The sides of the head are golden-brown. The rest of the under side as far as the tail coverts is rufous to golden brown, with black streaks on the breast, and with some black bars on the tail coverts. The under-wing coverts are buff. The wing and tail quills are less clearly banded than in the adult. The eyes are brown, the feet and cere yellow.
The primary feathers of this species are very long, reaching beyond the tip of the tail when folded. They are strongly curved and are quite flexible. The feet are also weak, the claws less sharply curved than most eagles.
Listen to the sound of Black Eagle
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The long and soft primaries must be an adaptation to assist the very slow flight, which help the bird in its detailed search of forest and grassy hillside for birds’ nests, the contents of which are one of its chief foods. The flexibility and length of the primaries permit exceptionally wide separation at their tips, which is a useful adaptation enabling the bird to maintain very low flying speeds. When seizing a bird’s nest it drops from flight on to the tree-tops, or drops suddenly on small animals on grassy hillsides.
The nest is built high up in a big tree, often one overgrown with creepers. It is a substantial structure – four feet across by one-and-a-half to two feet deep – made of small sticks, and lined with green leaves. Pairs often have two nests about a mile apart. Nest repair begins two to three months before egg-laying.
One egg is laid (two occasionally) – laying dates vary by latitude between November and May, but mostly during the cold dry season. The breeding season in India is long and irregular, and may be more so in the true tropical rain forest.
No details of the incubation behaviour and fledging period are available.
The talons, much less sharply curved than in most raptors, are an advantage when taking whole birds’ nests, from which the eagle consumes the contents at a later time
Video Black Eagle
copyright: Josep del Hoyo