The black-and-chestnut eagle (Spizaetus isidori) is a South American species of bird of prey in the family Accipitridae. It is sometimes called Isidor's eagle. It is often placed in the monotypic genus Oroaetus. However, recent genetic testing indicates that this species is fairly closely related to Spizaetus species and thus the species should be included in that genus. Description This is a fairly large eagle and very large raptor at in total length with a wingspan of . It is largest current member of the genus Spizaetus, with the smallest males somewhat larger than the largest female ornate hawk-eagles. Full grown weights for black-and-chestnut eagles have been reported as , making it among neotropic eagles around the same body size as the two largest Buteogallus and the black-chested buzzard-eagle, at least twice as heavy as other Spizaetus and slightly heavier than the notably longer crested eagle. Only the harpy eagle is considerably larger among all neotropical eagles, with most other eagles absent from the high elevation forest home of the black-and-chestnut eagle apart from the solitary eagle. For its genus and for many genera of forest-dwelling raptors in general, it has a proportionately short tail and proportionately long wings but still it is longer tailed and shorter winged than most true open country eagles. Females are notably larger as is typical in raptors, by about 4% to 14%, and longer tailed. The wing chord and tail length is and in males, respectively, and and in females. A small sample of these eagles measured in tarsus length. The talons of this species are very large and formidable for the size of the eagle, averaging in 6 females and in 6 males along the enlarged hallux claw (their main killing apparatus), thus nearly as large as a much bigger eagle such as a golden eagle. As an adult, this species is glossy black on the head and the back and a rich and somewhat streaky chestnut on the underside, much of the wing secondaries and even on its legs. The black-tipped white feathers on the wing primaries contrast strongly with the chestnut secondaries and underwing coverts. The adult's tail is grayish with a thick black subterminal band. Adult black-and-chestnut eagles have orange-yellow eyes and yellow bare parts but for the somewhat proportionately small gray bill. The juvenile bird is very different, being whitish over the head and body with a buffy wash