underneath and scaly grey-brown on the back and mantle, somewhat more extensive than in other whitish juvenile Spizaetus. The wings are whitish on juveniles where adults are chestnut and the remaining wing feathers of the juvenile have a much more varying black-and-white pattern. The tail of juveniles has two strong black bands. The juvenile’s eye is blue-gray, later becoming yellow before becoming orangish at maturity. Maturity is obtained gradually over four years, about average for a large eagle but nearly twice as long as some other Spizaetus species. Adult black-and-chestnut eagles are practically unmistakable, unless seen only dorsally and then can be distinguished from the black hawk-eagle by its larger, much bulkier frame and distinctive tail pattern on a conspicuously relatively shorter tail. Black-and-chestnut juveniles are more reminiscent of juveniles of both other Spizaetus species but are distinctly larger, bulkier and proportionately shorter tailed than both and each species has somewhat distinctive juvenile patterns on the wing primaries and tail. The black-and-white hawk-eagle is particularly far smaller and, unlike the ornate hawk-eagle, is not known to take up occasional residency in cloud forests. Also juvenile pale morph crested eagles can appear surprisingly similar in flight to juvenile black-and-chestnut eagles but are conspicuously longer tailed with a stronger barring pattern. Furthermore, there is little to no overlap with the other species of the genus as well as crested eagles due to the distinct habitat used by the black-and-chestnut. The solitary eagle is unlikely to be mistaken, being much broader winged and lacks all chestnut pigment, furthermore having an almost inverse tail pattern to adult black-and-chestnuts on a rather shorter tail. Unlike other crested raptors, it is reported that the crest of the black-and-chestnut eagle is held upright during calm periods of time and in flight and more likely to be held flat in stressful circumstances. Ecology Nest building is February and March, laying eggs in April and May and fledgling young by August and September. It builds a huge stick nest about 2 m (6.6 ft) across and 1 m (3.3 ft) deep. Clutches include 1 to 2 fledglings. At the nest area in some areas, adults primarily appeared to bring squirrels to feed their young. In Argentina, it was recorded that the female visited the nest more times and invested more time into nest building than males do. The female was responsible for the incubation and incubated every night in