Javan hawk-eagle (Nisaetus bartelsi)

Javan hawk-eagle (Nisaetus bartelsi) is a species of bird in the family Accipitridae. It is a medium-to-large, slender raptor, measuring 60–70 cm in length (from the tip of the beak to the tip of the tail). Its head is reddish-brown and features a prominent, tall crest consisting of 2–4 feathers—up to 12 cm in length—that are black with white tips.

N. bartelsi has a yellowish-brown nape, which can appear golden when struck by sunlight. The crown and the "mustache" (malar stripes) are black, while the back and wings are dark brown. The throat is whitish with a longitudinal black streak running down the center.



Moving downward toward the chest, black streaks spread across a pale yellowish-brown background. Further down, these transition into a pattern of dense, dark reddish-brown to brownish transverse bars against the pale, whitish feathers of the belly and legs. The legs are feathered down to near the base of the toes. The tail is brownish with four broad, dark transverse bands—clearly visible from below—and a thin white tip.

The irises are yellow or brownish, the beak is blackish, and the cere (the fleshy area at the base of the beak) and toes are yellowish. Juveniles have a light, wood-brown head, neck, and underparts, lacking any streaks or bars.

In flight, this hawk-eagle tends to appear more brownish, with the belly looking notably darker. Its call is a high-pitched, repetitive sound—"klii-iiw" or "ii-iiiw"—consisting of 1–3 syllables; it may also produce a rapid, high-pitched "kli-kli-kli-kli-kli."

This species is distributed across the island of Java; however, its current range is restricted to areas with primary forest and forested hilly regions located in the transition zone between the lowlands and the mountains. Most of these birds are found in the southern half of the island of Java. They are specialized to inhabit sloping terrain.

This eagle favors evergreen tropical rainforest ecosystems, ranging from coastal lowlands to lower and upper montane forests at elevations of up to 3,000 meters. In general, the species is highly dependent on primary forests for its habitat. While some individuals may use secondary forests for hunting or nesting, such areas are typically located in close proximity to extensive primary forests.

As a predator, it hunts from perches in tall trees. It is swift and agile, swooping down to seize various prey—found on tree branches or on the ground—including reptiles, birds, pigeons, junglefowl, squirrels, flying foxes, civets, and even young monkeys.

They build nests in tall trees, constructing them from a collection of leafy twigs placed on branches 20–30 meters above the ground. A single egg is laid and incubated for 47 days. The breeding season spans from January to June, with both parents participating in feeding their offspring.

The species is sparsely distributed. Despite having a wide range, the total population is estimated at only 137–188 pairs, or approximately 600–1,000 individual birds. This small population faces threats to its survival due to habitat loss. Furthermore, they are frequently hunted for the illegal wildlife trade, ending up on the black market as pets.

The IUCN classifies this species as EN (Endangered). The Indonesian government has designated it as a legally protected animal under Government Regulation Number 7 of 1999.

In 1820, van Hasselt and Kuhl collected two specimens of this bird from the Mount Salak region for the Leiden Museum; until the end of the 19th century, it was misidentified as the changeable hawk-eagle (Nisaetus cirrhatus). In 1908, Max Bartels brought back a specimen from Pasir Datar, Sukabumi. In 1924, Stresemann assigned the specific epithet bartelsi to this new taxon—in honor of Max Bartels—and classified it as a subspecies of the mountain hawk-eagle (Spizaetus nipalensis).

The bird became known internationally as Spizaetus nipalensis bartelsi until 1953, when Amadon proposed elevating its taxonomic rank, establishing it as a distinct species: Spizaetus bartelsi.

TAXON

Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Aves
Order: Accipitriformes
Family: Accipitridae
Subfamily: Aquilinae
Genus: Nisaetus Hodgson (1836)
Species: Nisaetus bartelsi Stresemann (1924)

SYNONYMS

Spizaetus bartelsi

VERNACULAR NAME

Arabic: أفياء جاوي - عقاب البازي الجاوي
Czech: Orel jávský
Dutch: Javaanse Kuifarend
English: Javan Hawk-Eagle
Finnish: Jaavanjalokotka
French: Aigle de Java
German: Javahaubenadler
Hindi: गरुड़ Garuda
Hungarian: Jávai vitézsas
Indonesian: Elang jawa, Garuda, Garuda Pancasila
Italian: Aquila dal ciuffo di Giava
Japanese: ジャワクマタカ
Java: Garuda, Lang Jawi
Lithuanian: Javinis peslinis erelis
Norwegian: Javaskogørn
Polish: Wojownik jawajski
Portuguese: Águia-de-java
Russian: Яванский хохлатый орёл
Slovak: Orlovec pralesný
Spanish: Águila azor de Java
Thai: ครูทผา - การูดา

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