Great Philippine eagle, monkey-eating eagle (Pithencophaga jefferyi)

The largest eagle in the world

The Philippine eagle is the largest eagle in the world, yet most people have never heard of it and, even worse, never will. Not only because of its exotic origin, but mostly owing to the extremely small wild population. The uncertain future of the Philippine eagle should remind of how many species disappear from the surface of the Earth, not only through evolution…

The world’s largest bird of prey

The largest eagle

Today we are taking you on a journey to the distant Philippines. On these islands rules a bird, which can easily be described as the world’s largest bird of prey – an exceptional heir and successor of the Haast’s eagle (Harpagornis moorei)…

Classification

• Kingdom: Animalia
• Phylum: Chordata
• Class: Aves
• Order: Accipitriformes
• Family: Accipitridae
• Genus: Pithecophaga
• Species: Pithecophaga jefferyi
• Names: Philippine eagle, great Philippine eagle, monkey-eating eagle

Areas of occurrence

Philippine eagle is endemic to the Philippine forests, living on the Luzon and Mindanao islands, in Samar and Leyte provinces. The largest population lives on Mindanao – between 82 and 233 breeding pairs.

It lives in the mountains of Sierra Made on Luzon and in close proximity to the stratovolcano Apo and the dormant volcano Kitanglad on the Mindanao island.

It prefers the highland deciduous woods, especially on steep slopes. It can also be found in the lowlands and in mountain ranges up to 1,800 meters (5,900 ft) above sea level. About 9,220 km² (3,560mi²) of the eagle’s habitat are old forest formations, while the total estimated area of the territory it appears in is about as large as 146,000 km² (56,000 mi²).

Characteristics

Philippine eagle is a bird with beautiful, long, brown feathers on its head, composing an impressive mane, resembling a lion’s mane. This specific plume reminds of a South American harpy eagle, though one must admit that the Philippine eagle is somewhat prettier 🙂 This dignified bird bears resemblance to a griffin for many bird-watchers.

It has a dark face, cream-brown neck and mane, the dorsal area is covered with magnificent dark brown feathers, while the bottoms of the wings are white. Strong, thick legs appear yellow and powerful talons are dark and highly curved, beak and eyes are of a greyish-blue color. Adolescent eagles are not entirely different from adults, only their dorsal feathers have bright edges.

Size

The body length ranges from 86 to 102 cm (2ft 9.9in – 3ft 4.2in), yet researches on several specimens have shown that the largest found male was 95 cm (3ft 1.4in) long, while the female was 105 cm (3ft 5.3in).

The largest bird of prey in captivity

The largest eagle kept in captivity measured 112 cm (3ft 8.1in), which makes this species the largest bird of prey in terms of length, right behind the extinct Haast’s eagle (Harpagornis moorei), for the similar-sized Argentavis (the largest wingspan in history) is identified as a scavenger.

However this specimen may not be a fair representation of a wild population, for in captivity it had a far easier food access, which allowed it to achieve such a grand size – same as the heaviest harpy eagle.

Weight

Philippine eagle weighs from 4.5 to 8 kg (10 – 18 lb), yet the average weight is lower, for females have a mean weight of about 6 kg (13lb), males – 4.5 kg (10 lb). The Philippine eagle dazzles with its wingspan, reaching 184 – 220 cm (72 – 87 in), with the width of a single wing ranging from 57.4 – 61.4 cm (23 – 24 in).

Tarsus, tail and beak

This Philippine bird has the longest tarsus (the body part linking the bird’s foot with the shin) among the whole Accipitridae family – it reaches from 12.2 to 14.5 cm (4.8 – 5.7 in), while the beak measures over 7 cm (2.76 in) on average. The tail is also long, as it grows up to 42 – 45.3 cm (16.5 – 17.8 in), while other sources state that it even reaches 50 cm (19.7 in) of length.

The sounds made by a Philippine eagle are loud and shrill, they resemble a whistle. Young eagles ‘yell’ for food with a series of high-pitched vocalizations.

Diet and hunting style

Diet

Throughout many years this animal was called a monkey-eating eagle in the Philippines, as it was believed that it eats monkeys exclusively (the only primate mammal living in the Philippines is a macaque subspecies – Macaca fascicularis philippensis), however, over time it turned out not to be true.

Most likely a reason for such an approach was finding undigested monkey remains in its stomach.

As the vast majority of predators, the Philippine eagle is opportunistic – it feeds on whatever is the easiest catch and whatever is most abundant in a given moment. As an apex predator, it eats many animals – from a 10-gram (0.022lb) bat to a 14-kg (31 lb) Philippine deer (Rusa marianna).

A diet depends on the region

Its diet highly depends on the inhabited region, as on the Luzon and Mindanao islands the bird encounters two different types of fauna, e.g. the Philippine flying lemur (Cynocephalus volans) being an element of the Mindanao eagles’ diet do not live in Luzon – an island abundant with monkeys, birds, flying foxes (Pteropus), enormous Northern Luzon giant cloud rats (Phloeomys pallidus), which can weigh twice as much as flying lemurs and reptiles (large snakes and lizards).

Philippine eagle generally prefers the abovementioned flying lemurs (in their habitat regions), it can see prey in a small ungulate mammal or even a human…

The Mindanao predators’ menu consists of macaques, flying squirrels (Pteromyini), Asian palm civets (Paradoxurus hermaphroditus), tree squirrels, giant fruit bats of the Megachiroptera suborder, rats, birds (owls and hornbills), reptiles.

Several cases of snatching a wild boar and a small dog were documented.

Hunting style

Philippine eagle uses two hunting techniques: the first one is based on a stationary observation of potential prey from a tree branch, the other one involves cyclic flying between the hunting spots. Using the latter, the eagle flies down to lower and lower branches, seeking prey. If one does not show up, the bird returns to the highest vantage point and repeats the whole ‘ ritual’.

This method proves most effective when hunting for flying lemurs and flying squirrels as, being nocturnal animals, they use camouflage during the day to prevent being attacked by predators.

Pairs of Philippine eagles often act as a hunting team during monkey hunts: one distracts the monkeys’ attention, while the other strikes from behind.

As macaques are often of similar size to Philippine eagles, they are sometimes a difficult and dangerous opponent: eagles are regularly left with a broken leg after the scuffle.

Breeding

Females reach sexual maturity being at least 5 years old, males at 7 years of age. Like the majority of the Accipitridae family, the Philippine eagle is a monogamist. A pair once bound together remains in a relationship until the end of their lives, if one partner dies, the other pursues a new one.

The mating process begins with nest building; after having done all the work the Philippine eagle remains in close proximity to the newly-built home.

The moment a male spots a female, an aerial chase begins: after the ‘catch’, the male demonstrates its talons. The presentation is accompanied by loud calls.

Another signal of breeding readiness is bringing the padding material to the nest, after the whole ritual copulation takes place, repeatedly inside and outside the nest.

The hatching season normally starts in July, though there are some differences depending on the inhabited region, precipitation and the predatory population in a given area.

Nest

The nest is made of branches in the spreading tree canopies (often even 30 meters high). The inside of a hatching nest, which diameter reaches 1.5 m, is lined with green leaves. One net may be used multiple times by the same pair.

Offspring

A female usually lays one egg in the late afternoon or at dusk, though cases of two eggs in one hatch were also recorded. If an egg remains dead, or a nestling dies soon after hatching, the pair will try to have another baby in the following year (normally hatching takes place once every two years).

Incubation lasts 58-68 days (62 on average), both the mother and father take part in it: a female usually incubates eggs during the day, the male takes over the responsibility at night. Parents also feed the newly hatched chick, protect it from sunlight and rain throughout the next 7 weeks. The offspring grows feathers after 4-5 months, and they are looked after for 20 months total.

Population

The population of the Philippine eagle is estimated to oscillate between 180 – 500 eagles. Therefore it practically is a critically endangered species…

Detailed characteristic/size

Philippine eagle (Pithecophaga jefferyi)

• Length:
  • in the wild: 86 -102 cm (2ft 9.9in – 3ft 4.2in)
  • longest in captivity: 112 cm (3ft 8.1in)
  • the largest male was 95 cm (3ft 1.4in) – in the wild
  • the largest female was 105 cm (3ft 5.3in) – in the wild
• Body mass: 4.5 – 8 kg (10 – 18lb)
  • average female mass: 6 kg (13 lb)
  • average male mass: 4.5 kg (10 lb)
• Wingspan: 184 – 220 cm (72 – 87 in)
• Wing width: 57.4 – 61.4 cm (23 – 24 in)
• Tarsus length: 12.2 to 14.5 cm (4.8 – 5.7 in)
• Beak length: over 7 cm (over 2.76 in)
• Tail length: 42 – 45.3 cm (16.5 – 17.8 in), max. 50 cm (19.7in)

Philippine eagle, monkey-eating eagle – interesting facts

• Sexual dimorphism in terms of size has not been confirmed, yet it is supposed that males are about 10% smaller than females. Among many large species of the Accipitridae family the size difference between adult males and females may exceed 20%.
• In some areas, 90% of these eagles’ diet was the Philippine flying lemur.
• A monkey-eating eagle’s nest is usually located higher than 30 m (98 ft) above ground.
• 8 – 10 days before laying eggs female falls into a specific lethargy, the so-called egg lethargy. In this state, the bird does not eat, drinks large amounts of water and keeps wings in a descending position.
• The nest’s sole threat is human activity, for both macaques and civets, being predatory, clearly avoid the eagles’ breeding territories.
• Philippine eagle is the Philippines’ national animal since 4 July 1995.
• Philippines – the only country in the world where this species lives – has one of the highest deforestation rates in the world, and such actions have the highest impact on the gradual extinction of the Philippine eagle.
• Though a Philippine eagle may be considered the largest eagle, due to its habitat preferences (forest areas) it does not have the largest wingspan. More information considering this matter may be found in the article: The largest eagles Top 10.

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