Black-and-chestnut Eagle

Quick Facts

  • Scientific Name: Spizaetus isidori
  • Spanish Name: Águila pechinegra
  • Family: Accipitridae
  • Known Nicknames: Isidor's Eagle, Black-and-chestnut Hawk-Eagle
  • Average Length: 63–74 cm / 25–29 in
  • Average Weight: 1.6–2.4 kg / 3.5–5.3 lb
  • Wingspan: 147–168 cm / 58–66 in
  • Key Feature: Contrasting black head, back, and wings with rich chestnut belly and underwing coverts
  • Primary Diet: Carnivore (primarily arboreal mammals and birds)
  • Range: Andes of Venezuela, Colombia, Ecuador, Peru, and Bolivia
  • Habitat: Subtropical and temperate montane cloud forest
  • Social Structure: Solitary or in pairs
  • Nesting/Breeding: Large stick nest in emergent tree
  • Conservation Status: Endangered (EN)
  • Population Trend: Decreasing

The Black-and-Chestnut Eagle (*Spizaetus isidori*) is a magnificent and elusive raptor of the South American Andes, renowned for its striking dual-toned plumage and formidable power. Its head, neck, and underparts are a rich, deep chestnut, sharply contrasting with its jet-black back, wings, and long, banded tail. A unique feature is its prominent, shaggy crest of feathers that can be raised or lowered, giving it an expressive, regal profile. As one of the largest forest eagles in its range, it possesses exceptionally broad, rounded wings and powerful talons adapted for hunting large birds and mammals like monkeys and sloths within dense montane cloud forests. This specialized predator is a vital, yet increasingly threatened, indicator of healthy, intact high-altitude ecosystems.

Fun Facts

Despite its name, the black-and-chestnut eagle is not entirely black and chestnut; its striking white belly and leg feathers create a dramatic contrast, making it one of the most visually distinctive raptors in the Andes. It has an unusual hunting tactic: rather than soaring high, it often hunts from a concealed perch within the cloud forest canopy, then crashes through dense foliage to ambush prey like monkeys and large birds. A quirky behavior is its tendency to “play” with sticks or leaves in its talons while perched, a seemingly idle habit that may help sharpen its grip. Remarkably, it can rotate its head nearly 270 degrees, like an owl, to scan for threats or prey without moving its body—a rare adaptation among eagles.

Habitats & Distribution

This raptor inhabits humid montane forests and cloud forests, typically at elevations between 1,500 and 3,000 meters. It prefers steep, rugged terrain with dense canopy cover, often near forest edges or clearings. Its geographical range is restricted to the northern Andes, stretching from western Venezuela through Colombia, Ecuador, and into northern Peru. Isolated populations may also occur in the Sierra Nevada de Santa Marta of Colombia.

Behaviours & Reproduction

The Black-and-chestnut Eagle is a solitary and territorial raptor, with pairs maintaining large home ranges in montane forests. Mating is monogamous and likely lifelong, with courtship involving aerial displays such as steep dives and mutual soaring. The breeding season varies regionally but typically coincides with prey availability. The pair builds a large stick nest high in a tall tree, often reused and enlarged over successive years. The female usually lays a single egg, an uncommon clutch size for eagles, which may be an adaptation to the challenging high-altitude environment where food resources are limited. Both parents share incubation and chick-rearing duties, with the male provisioning the female and later the eaglet. The fledgling period is prolonged, often exceeding three months, and the young may remain dependent on the parents for several additional months, a strategy that ensures high survival rates for the single offspring.

Diet

The Black-and-chestnut Eagle is a specialized predator of medium-to-large arboreal mammals and birds, primarily hunting within the dense montane forests of the Andes. Its diet centers heavily on monkeys, such as woolly monkeys, howler monkeys, and capuchins, which it snatches from the canopy with powerful talons. It also preys on coatis, kinkajous, sloths, and large birds like guans and toucans. An interesting dietary fact is that this eagle often targets prey nearly as large as itself, requiring immense strength and agility to subdue them in the trees. Additionally, unlike many other eagles that hunt from a perch, it frequently soars low over the forest canopy, using its keen eyesight to spot movement, and it has been observed to follow troops of monkeys for long distances before striking.

Colors

The Black-and-chestnut Eagle has a dark brownish-black head, back, and wings, contrasting sharply with a deep chestnut breast, belly, and leg feathers. Its tail is boldly banded with black and gray, while the cere and feet are bright yellow. Juveniles are distinctly different, with a white head and underparts heavily streaked with black, providing camouflage against the dappled light of its cloud forest habitat.