Black-and-chestnut Eagle (Spizaetus isidori)

Black-and-chestnut Eagle

[order] ACCIPITRIFORMES | [family] Accipitridae | [latin] Spizaetus isidori | [authority] Des Murs, 1845 | [UK] Black-and-chestnut Eagle | [FR] Aigle d’Isidore | [DE] Isidoradler | [ES] Aguila poma | [NL] Andeskuifarend


Monotypic species


The genus Spizaetus is a genus of ten species. It is a tropical genus of forest eagles, closely related to a couple of other genera of specialised eagles. There is a large variation in size – members of this genus range from small to rather large eagles, and are variable in their proportions. The common thread is to be found in their basic outline – they are all slender birds with short, rounded wings and rounded tails (well adapted to manoeuvre through dense forest). Most, but not all, are crested.

Physical charateristics

In the adult, the head, throat and upper parts are a slightly glossy black. The crown feathers are slightly pointed and have shiny shafts. The pointed crest is about eight to ten centimetres in length. The tail is mostly pale grey with white markings, and a black band at the end. The primaries are grey with black ends, the secondaries mostly black above; below with broad black tip. There is a pattern of barring along both primaries and secondaries of reducing depth of blackness on a pale grey background. The throat is black; the rest of its under parts dark chestnut, fading to paler chestnut brown, with prominent, scattered, black streaks (more prominent on upper breast where they blend with black throat). The eyes are orange-yellow, the bill black becoming horn-colour towards its base.
The immature is more buff or pale grey around the crown and the sides of its head. The crest feathers, which are almost as long as in the adult, are black with paler edges and tips. Its back and wing coverts are variegated – pale brown/grey with scattered darker streaks. The tail is marbled grey and white with a narrow white tip, a sub-terminal black band about an inch and a quarter wide and two narrower, uneven black bars, and a third concealed one. The primaries are marbled grey, white towards the inner edge and below barred with black; the secondaries are similar, but darker and with white tips. Below it is white with a few scattered dark brown streaks on the breast and sides and a few pale chestnut stains on breast, sides and flank. The eyes, at first clear blue-grey, become yellow at about three months. Full adult plumage is not attained until about four years.

Listen to the sound of Black-and-chestnut Eagle

[audio: Eagle.mp3]

Copyright remark: Most sounds derived from xeno-canto

wingspan min.: 170 cm wingspan max.: 180 cm
size min.: 60 cm size max.: 80 cm
incubation min.: 0 days incubation max.: 0 days
fledging min.: 110 days fledging max.: 130 days
broods: 1   eggs min.: 1  
      eggs max.: 1  


South America : Venezuela to Northwest Argentina. This species has an extensive but narrow and altitudinally restricted linear distribution on the coastal ranges of north-west Venezuela (Carabobo and Aragua) and north-east Colombia (Santa Marta Mountains), and from the subtropical slopes of the Andes from Venezuela (Merida and Perija Mountains) through Colombia (Serrana de los Churumbelos), Ecuador and Peru to west-central Bolivia and north-west Argentina.


Generally found in heavy Andean sub-tropical and perhaps also temperate rain forest, it ventures on occasion to lower and to higher levels. It is found in some areas that have been partially cleared or logged, but probably only because large areas of virgin forest in the sub-tropical zone are an increasingly rare sight. It is sometimes seen gliding along above the trees hunting, but spends a good deal of its time perched upright, often on one leg, hidden in a large tree or sometimes on a dead stump. It is not a bird that is easy to see regularly.


The nest is large, six or more feet across and three feet in depth, growing over several seasons of use. It is usually close to the top of a tall tree, often an oak. Some of the branches for the nest are collected by seizing in the feet and snapping it off. Branches may be collected from as far away as a kilometre. The green leafy branches are bent around and worked into the nest structure. It may also pick up some dead branches. Nest construction start in February or March, and takes about two months to complete. In the humid sub-tropics of the eastern Andes the early mornings are often fair, followed by damp fog and heavy rain. The eagles usually build their nests here on eastern-facing slopes to take advantage of the morning sun. Only one egg is laid. The male carries out most of the hunting while the female is incubates and cares for the young, until the latter is well grown. Squirrels are a favourite food during the first weeks of the eaglet?s life. Sometimes the male arrives with prey with great speed on half-furled wings from higher up the mountain. At other times he is obviously exhausted by his efforts and sits near the nest with his wings hanging at the sides. As the young grows the parents are less in evidence at the nest. The young may remain in the nest tree for a few days after it can fly and is seen with its parents and is doubtless fed by them for some time thereafter. Green small branches are brought to the nest from time to time: The young is believed to fly when about four months old.

Feeding habits

This bird has very powerful legs and talons, indicating a preference for good-sized prey. Living on heavily forested mountain slopes, its large size and long and broad wings indicate that it may hunt extensively in the crown of the forest for squirrels, monkeys, other medium-sized arboreal mammals and slow flying large arboreal birds.
It sometimes shows a strong preference for native poultry, which are taken on the ground, and it may catch quite a lot of its prey there.
During the breeding season, when the male is hunting for himself, his mate, and young, his tail becomes badly worn, by plunging through branches in pursuit of prey.


This species has been uplisted to Vulnerable as it has a small population, with all sub-populations believed to number fewer than 1,000 mature individuals, which is undergoing continuing decline as a result of the destruction of its montane forest habitat. Further research is required to elucidate threatening processes and quantify their resulting effects on population trends.
It apparently requires at least part of its home range to include undisturbed primary forest, which has been subject to huge losses in many parts of its extensive range, primarily due to conversion for agriculture. Persecution has been recorded on farms surrounding the Yalcones Nature Reserve, Colombia, as the species predates chickens, though it is not known to what extent this poses a threat. It is thought to be rare and patchily distributed but its status is very poorly known,3. A recent population estimate indicated that the total population may not exceed 1,000 individuals, however, the Venezuelan population is estimated to be in the low hundreds, a maximum of 200 individuals are estimated to reside in Ecuador, and a large stretch of suitable habitat on the eastern slopes of the Andes in Colombia, from Huila to Meta department, is also thought to hold a few hundred individuals. Although the population in Argentina may be small, there are further populations in Colombia and an unquantified number in Peru and Bolivia, suggesting that, whilst remaining rare, the global population is still larger than 1,000 individuals. However, given habitat loss throughout its range, the population is considered to be declining.
Black-and-chestnut Eagle status Vulnerable



Distribution map

Black-and-chestnut Eagle distribution range map

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