It is found in mountainous or hilly forests, at elevations between 600 m and 2,200 m. The frequent reports from lowlands are usually misidentifications of another species, usually the common black hawk or great black hawk; no reports from lowlands have been confirmed.

Very little is known about its diet, other than that it appears to have often been predating large snakes and one adult pair was seen hunting deer fawns.

The adult solitary eagle is uniformly dark gray, often appearing black, with white markings on the tail.

[3] With a body mass of approximately 3 kg (6.6 lb), it appears to rival its similarly-weighted sister species, the Chaco eagle, as one of the larger living members of the Buteoninae subfamily, although the black-chested buzzard-eagle is similar or only marginally smaller in weight, while large Milvini from the genus Haliaeetus and Icthyophaga (such as the Steller's sea eagle) can be significantly larger.

Recent DNA studies have shown that the solitary eagle is closely related to the black-hawks.