The 1st European to discover the species was the English explorer and naturalist John Whitehead in 1896, who observed the bird and whose servant, Juan, collected the 1st specimen a few weeks later. The skin of the bird was sent to William Robert Ogilvie-Grant in London in 1896, who initially showed it off in a local restaurant and described the species a few weeks later.
Upon its discovery, the Philippine Eagle was 1st called the monkey-eating eagle because of reports from natives of Bonga, Samar, where the species was 1st discovered, that it preyed exclusively on monkeys; from these reports it gained its generic name, from the Greek pithecus and phagus ("eater of"). The specific name commemorates Jeffery Whitehead, the father of John Whitehead. Later studies revealed, however, that the alleged monkey-eating eagle also ate other animals, such as colugos, civets, large snakes, monitor lizards, and even large birds, such as hornbills. This, coupled with the fact that the same name applied to the African Crowned Eagle and the Central and South American Harpy Eagle, resulted in a presidential proclamation to change its name to Philippine Eagle in 1978, and in 1995 was declared a national emblem. This species has no recognized subspecies.
Apart from Philippine Eagle and Monkey-eating Eagle, it has also been called the Great Philippine Eagle. It has numerous local names, including agila , haribon, haring ibon ("king bird") and banog ("kite").
A study of the skeletal features in 1919 led to the suggestion that the nearest relative was the Harpy Eagle. The species was included in the subfamily Harpiinae until a 2005 study of DNA sequences which identified them as not members of the group, finding instead, that the nearest relatives are snake eagles , such as the Bateleur. The species has subsequently been placed in the subfamily Circaetinae.
The Philippine Eagle's nape is adorned with long, brown feathers that form a shaggy crest. These feathers give it the appearance of possessing a lion's mane, which in turn resembles the mythical griffin. The eagle has a dark face and a creamy-brown nape and crown. The back of the Philippine Eagle is dark brown, while the underside and underwings are white. The heavy legs are yellow, with large, powerful dark claws, and the prominent large, high-arched, deep beak is a bluish-gray. The eagle's eyes are blue-gray. Juveniles are similar to adults except their upperpart feathers have pale fringes.
The most frequently heard noises made by the Philippine Eagle are loud, high-pitched whistles ending with inflections in pitch. Additionally, juveniles have been known to beg for food by a series of high-pitched calls.
The Philippine Eagle is endemic to the Philippines and can be found on four major islands: eastern Luzon, Samar, Leyte, and Mindanao. The largest number of eagles reside on Mindanao, with between 82 and 233 breeding pairs. Only six pairs are found on Samar, two on Leyte, and a few on Luzon. It can be found in Northern Sierra Madre National Park on Luzon and Mount Apo and Mount Kitanglad National Parks on Mindanao.
The species' flight is fast and agile, resembling the smaller hawks more than similar large birds of prey.
Juveniles in play behavior have been observed gripping knotholes in trees with their talons and, using their tails and wings for balance, inserting their heads into tree cavities. Additionally, they have been known to attack inanimate objects for practice, as well as attempt to hang upside down to work on their balance. As the parents aren't nearby when this occurs, they apparently don't play a role in teaching the juvenile to hunt.
Life expectancy for a wild eagle is estimated to be from 30 to 60 years. A captive Philippine Eagle lived for 41 years in Rome Zoo, and it was already adult when it arrived at the zoo. However, wild birds on average are believed to live shorter lives than captive birds.
The Philippine Eagle was known initially as the Philippine Monkey-Eating Eagle because it was believed to feed on monkeys almost exclusively; this has proven to be inaccurate. This may be because the 1st examined specimen was found to have undigested pieces of a monkey in its stomach. Like most predators, the Philippine Eagle is an opportunist that takes prey based on its local level of abundance and ease. It is the apex predator in its range.
Philippine Eagles primarily use two hunting techniques. One is still-hunting, in which it watches for prey activity while sitting almost motionlessly on a branch near the canopy. The other is perch-hunting, which entails periodically gliding from one perch to another. While perch-hunting, they often work their way gradually down from the canopy on down the branches and, if not successful in find prey in their initial foray, will fly or circle back up to the top of the trees to work them again. Eagles in Mindanao often find success using the latter method while hunting flying lemurs, since they are nocturnal animals which try to use camouflage to protect them by day. Eagle pairs sometimes hunt troops of monkey cooperatively, with one bird perching nearby to distract the primates, allowing the other to swoop in from behind, hopefully unnoticed, for the kill. Since the native macaque is often around the same size as the eagle itself, it is a potentially hazardous prey, and eagles have been reported to suffer broken leg due from a fall after struggling and fell along with a large male monkey.
The complete breeding cycle of the Philippine Eagle lasts two years. The female matures sexually at five years of age and the male at seven. Like most eagles, the Philippine Eagle is monogamous. Once paired, a couple remains together for the rest of their lives. If one dies, the remaining eagle often searches for a new mate to replace the one lost.
The beginning of courtship is signaled by nest-building, and the eagle remaining near its nest. Aerial displays also play a major role in the courtship. These displays include paired soaring over a nesting territory, the male chasing the female in a diagonal dive, and mutual talon presentation, where the male presents his talons to the female's back and she flips over in midair to present her own talons. Advertisement displays coupled with loud calling have also been reported. The willingness of an eagle to breed is displayed by the eagle bringing nesting materials to the bird's nest. Copulation follows and occurs repeatedly both on the nest and on nearby perches. The earliest courtship has been reported in July.
Both sexes help feed the newly hatched eaglet. Additionally, the parents have been observed taking turns shielding the eaglet from the sun and rain until it is seven weeks old. The young eaglet fledges after four or five months. The earliest an eagle has been observed making a kill is 304 days after hatching. Both parents take care of the eaglet for a total of 20 months and, unless the previous nesting attempt had failed, the eagles can breed only in alternate years. Even nests have no predators other than humans, as even known nest predators such as palm civets and macaques are likely to actively avoid any area with regular eagle activity.
In 2010, the IUCN and BirdLife International listed this species as critically endangered. The International Union for the Conservation of Nature believes between 180 and 500 Philippine Eagles survive in the Philippines. They are threatened primarily by deforestation through logging and expanding agriculture. Old-growth forest is being lost at a high rate, and most of the forest in the lowlands is owned by logging companies. Mining, pollution, exposure to pesticides that affect breeding, and poaching are also major threats. Additionally, they are occasionally caught in traps laid by local people for deer. Though this is no longer a major problem, the eagle's numbers were also reduced by being captured for zoos.
The diminishing numbers of the Philippine Eagle were 1st brought to international attention in 1965 by the noted Filipino ornithologist Dioscoro S. Rabor, and the director of the Parks and Wildlife Office, Jesus A. Alvarez. Charles Lindbergh, best known for crossing the Atlantic alone and without stopping in 1927, was fascinated by this eagle. As a representative of the World Wildlife Fund, Lindbergh traveled to the Philippines several times between 1969 and 1972, where he helped persuade the government to protect the eagle. In 1969, the Monkey-eating Eagle Conservation Program was started to help preserve this species. In 1992, the 1st Philippine Eagles were born in captivity through artificial insemination; however, not until 1999 was the 1st naturally bred eaglet hatched. The 1st captive-bred bird to be released in the wild, Kabayan, was released in 2004 on Mindanao; however, he was accidentally electrocuted in January 2005. Another eagle, Kagsabua, was released March 6, 2008, but was shot and eaten by a farmer. Killing this critically endangered species is punishable under Philippine law by 12 years in jail and heavy fines.
The Philippine Eagle was officially declared the national bird of the Philippines on 4 July 1995 by President Fidel V. Ramos under Proclamation No. 615. This eagle, because of its size and rarity, is also a highly desired bird for birdwatchers.
The Philippine Eagle has also featured on at least 12 stamps from the Philippines, with dates ranging from 1967 to 2007. It was also depicted on the 50-centavo coins minted from 1981 to 1994.
Historically, about 50 Philippine Eagles have been kept in zoos in Europe , the United States, and Japan. The 1st was a female that arrived in London Zoo in August 1909 and died there in February 1910. The majority arrived in zoos between 1947 and 1965. The last outside the Philippines died in 1988 in the Antwerp Zoo, where it had lived since 1964 (except for a period at the Planckendael Zoo in Belgium). The 1st captive breeding was only achieved in 1992 at the facility of the Philippine Eagle Foundation in Davao City, Mindanao, the Philippines, which has bred it several times since then.