New Guinea Eagle

The Papuan eagle is an elusive forest dweller. Despite old claims that it soars, even claims that it does so frequently, evidence indicates it never engages in soaring flight. Typically this species is known to perch inconspicuously in thick canopy and can be fairly difficult to see as it often slips away quietly, seemingly to avoid human detection. Due to its occasional tendency to vocalize at night, large eyes and almost owl-like facial area, it was projected that this species may be an occasional nocturnal hunter. However, the Papuan eagle has never been proven to hunt by night and is now thought to be a diurnal hunter like other eagles. The Papuan eagle is a powerful hunter, who uses the still or perch hunting style typical of many forest raptors, gliding from often routine perch sites inconspicuously as possible within the forest. Flights between hunting perches are up to 1,500 m (4,900 ft) but usually as little as 50 to 60 m (160 to 200 ft). This raptor is said to detect terrestrial prey partially through sound by listening for movement in the undergrowth and, while hunting, often bobs its head side to side and turns it at peculiar angles, seeming to be getting a fix on the prey's location, before dropping down. More unconventional hunting styles have been incorporated where the eagle clamors about from branch to branch, stopping to examine several holes, crevices and tearing into clumps of epiphytes. Sometimes Papuan eagles will also shake foliage to force small mammals to poke their heads out. This hunting method is reminiscent of unrelated accipitrids such as harrier-hawks and crane hawks, which also possess unusually elongated leg morphology in a possible case of convergent evolution, but the Papuan eagle lacks the unusual leg joints that allows those raptors to bend their legs multiple directions. The Papuan eagle is also known to spend a fair amount of time on the ground and to run with considerable agility and surprising speed, apparently whilst hunting for prey such as megapodes. The preferred prey appears to be a wide range of mammals. Regularly reported as primary prey are phalangers, tree-kangaroos, common ringtail possums, Dorcopsis and Dorcopsulus as well as woolly rats and giant naked-tailed rats. Phalangers or Kapul in a local language (although this name may sometimes apply to any marsupials), hence its alternative name, are often considered the most important prey. One food study in Crater Mountain Wildlife Management Area reinforced the primary importance of phalangers, as more than half of 29 prey items were these marsupials. However, a different study of the same wildlife management area showed a preference for Dorcopsulus forest wallabies, which comprised 6 of 10 prey items. However, data do indicate the Papuan eagle is an opportunistic predator and can take a wide range of birds including pigeons and doves, hornbills, cockatoos, megapodes and cassowaries. Additionally, incidents of predation on reptiles such as snakes and monitor lizards are known. Additionally, Papuan eagles have been known to hunt small dogs and young pigs. Singing dogs, established exotic wild animals analogous to Australia's dingos, are known to steal the bird's kills; in turn, the canids are part of the bird's diet. An incident of apparent act of predation by a Papuan eagle on a small child has been considered "thought authentic" by some authors and "very dubious" by others. Much of the recorded prey of Papuan eagles is fairly large, most species targeted by them weighing in adults 0.5 to 1 kg (1.1 to 2.2 lb) or considerably more, and the phalangers often thought to be preferred in their diet can average up to 6 kg (13 lb) in adults depending on species. Similarly, a Matschie's tree-kangaroo weighing 6 kg (13 lb) was recorded as prey of Papuan eagles. Even larger prey such as dwarf cassowary, which would weigh at least 13.5 kg (30 lb), have also been recorded. The Papuan eagle was thought to become the top predator of the island after the extinction of local giant monitor lizards and possibly large carnivorous marsupials. It is not known how Papuan eagles co-exist with the similarly sized Gurney's eagles, which also frequents rainforest and appears to select somewhat similar prey, but the Gurney's seems more prone to appearing in lower elevation forests (i.e. reportedly very rare above 1,500 m (4,900 ft) and more likely to visit forest openings. Furthermore, the Gurney's eagle hunts in flight at or slightly above the canopy level (in keeping with its considerably longer wings than the Papuan), very different from any foraging mode utilized by the Papuan eagle. Very little is known about breeding or pairing behaviour in the Papuan eagle. What it is known suggests it is a typically solitary raptor and forms presumably stable breeding pairs. It appears to breed largely in the dry season, such as April to November. A specimen in breeding condition was recorded in June, actively nest building in April–May and having large nestlings in August. Large, emergent trees appear to be preferred, with some genera the eagles have been known to nest being Eugenia, Syzygium and Aglaia. Usually, trees selected are on a slope and the nest will be placed on a very large one right near the canopy, often over 30 m (98 ft) above the ground. Nests in one study were found to be in trees an average of 8.7 m (29 ft) taller than the surrounding trees in the forest, with fewer lower branches and a high tree diameter. Their nests are invariably located deep within the forest. Nests are often re-used in subsequent years. Papuan eagle nests are enormous, ranging up to 3 m (9.8 ft) in both height and diameter. Nests are often place over the top of epiphytes and moss. Based on the fact that not more than one nestling nor the remnants of more than one egg have ever been found in a Papuan eagle nest, it is assumed that they lay only a single egg but other details of the egg-laying, incubation, nestling and fledgling process in this species are not known to date. Furthermore, some evidence suggests that they may only be able to breed every other year.

The Papuan eagle is endemic to New Guinea. It has been seen in almost every part of the island, from peninsular Indonesian Papua in the west to throughout the nation of Papua New Guinea in the east. The main native habitat inhabited by Papuan eagles are undisturbed tropical rainforests. However, they will also utilize gallery forests, monsoon scrub forest and dry woodland. The species even sometimes turning up in forest edge and relatively open areas such as gardens but more extensive research that this is extraordinarily rare if it does even occur. They can live at several elevations from sea level up to regularly 2,000 m (6,600 ft), but occasionally have reported at elevations ranging from 3,200 to 3,700 m (10,500 to 12,100 ft). At times it has been considered a bird that prefers steeper sloped or ridged parts of the forest.

While there have probably never been high densities of the Papuan eagle, evidence indicates that they are declining rapidly. Two different estimates posited similar total numbers, which put the number of Papuan eagles at between 1,500 and 15,000 individuals, but it is not known if this describes all individuals or merely just the breeding population, but it is certain to be a very rough estimate. It is possible that the entire population is considerably under 10,000 individuals. A number of well-known threats (most shared by similar raptor species) are known, particularly deforestation. There is no evidence that the Papuan eagle is adaptable to opening of forests and the eagles appear to abandon areas especially where logging roads have been cut into the forests. Some hunting occurs for this species' feathers which are used in ceremonies on occasion. These feathers were known to historically be highly prized possessions, although the Papuan eagle may also be shot or otherwise killed out of competition for bushmeat with local people. Evidence suggests that the active killing of Papuan eagles is quite ongoing well into the 21st century, and is probably entirely unsustainable given the already low population size. The Papuan eagle is evaluated as Vulnerable on the IUCN Red List of Threatened Species. It is listed on Appendix II of CITES.