Philippine Eagle Biology and Ecology

The Philippine Eagle (Pithecophaga jefferyi) is a giant forest raptor endemic to the Philippines. It is considered one of the largest and most powerful eagles in the world. Unfortunately, it is also one of the world's rarest and certainly among its most critical endangered vertebrate species. The eagle is known to be geographically restricted to the islands of Luzon, Samar, Leyte and Mindanao.

A. Breeding Biology

Philippine eagles are monogamous and they bond for life. But contrary to claims that they opt to remain unpaired in the death of their mate, evidences from natural pairing techniques and data from all other raptors indicate that they take in new mates as replacement. Females reach sexual maturity at around five years and males, at seven.

1. Courtship

Increased aerial displays, frequent stay near the nest and nest-building activity mark the start of the courtship period. In a study of a pair in 1999, courtship began as early as July. Aerial displays such as mutual soaring (paired soaring flight over the nesting territory), dive chase (diagonal drop by the female with the male trailing in pursuit), and mutual talon presentation (male extending talons to female's back with the female flipping over to present its talons) were documented. The pair also performed cruising flights over the territory, and did frequent advertisement displays couple0d with vigorous calling. Delivery of nesting materials, although aimed at building nest, can be a form of display to signal readiness to breed. Repeated copulation on nest and nearby perches marks the peak of courtship. Besides ensuring successful fertilization, frequent copulation is also interpreted as another means to strengthen pair bond. (click here to view illustrations)

Although different in few details, the courtship behavior observed in this particular pair is generally similar to most diurnal raptors. Courtship displays are expected to aid in the establishment and defense of a nesting territory, attraction of a suitable mate, and the establishment of a strong pair bond, all which are necessary for successful breeding.

2. Timing of Breeding

Data from nesting pairs in Mindanao suggest that the nesting (egg-laying) season can start in September and may extend up to February of the following year. But in Luzon, it is between mid-December to mid-January. The factors responsible for seasonal timing of breeding are not known. However, rainfall patterns, such as the case in Luzon where the periods from September to November are peak typhoon season thus would not be advantageous for egg-laying, as well as the seasonal abundance of the prey have been suggested as possible environmental factors that trigger breeding. A complete breeding cycle, from courtship until the young eagle leaves the parents' territory, lasts two years.

3. Egg-laying

Observation of captive females revealed that as egg laying draws near, the female appears to be sickly and would not take food for as long as 8 to 10 days. They have drooping wings, takes up a lot of water, continually do calls and builds nest. This condition is called "egg lethargy". After this phase, the female lays one egg during the late after noon or at dusk.

4. Incubation, nestling and post-fledgling         

Incubation lasts 58 to 68 days. Both the male and the female incubate the egg but the female has a greater share of the daytime, and apparently does all of nighttime, incubation. The female spent about two thirds of the incubation up to the early nestling period. After which, both hunt and feed the growing eaglet until independence. In one nest observed, the adults take turn brooding the young and covering it from the sun and the rain. But this ceased when the chick was left on its own in the nest when it was seven weeks old and thereafter. Once the egg is hatched, the eaglet will stay in the nest or about 5.5 months. The parents will take care of it for about 17 months until it leaves its parents territory in search of a vacant habitat.

Recent detailed observation gave revelations about play behavior in a juvenile Philippine Eagle. It was seen observing tree cavities and grasping the rim of knotholes using its tail as props and wing for balance while poking its head into the cavity. The young eagle also hangs itself upside down perhaps as an exercise in balance and was also seen doing mock attacks of inanimate objects on the ground or among tree crowns. All of these were done in the absence of the parents, which indicate that juveniles seem to learn hunting without parental intervention.

The table below summarizes the patterns of juvenile development as observed by Kennedy (1985).

5.  Longevity

The Philippine Eagle is a long-lived species. A captive bird in Rome Zoo was received full grown in 1934 and died in 1976, making it at least 41 years old at death. A male eaglet at the Philippine Eagle Center arrived as a young bird in 1969 and it's still alive and that makes it about 34 years old. It is still unknown how old eagles get in the wild. But based on the fact that wild birds face the many exigencies of the forest environment which is rather absent in the captive conditions, wild birds may live shorter than captive birds.

Another endangered avian

The Mindoro Tarictic Hornbill, another endangered wildlife from the island of the Tamaraws.

Tarictics are hornbills, large mystifying birds with distinctly shaped bills belonging to the family Bucerotidae.

There are four similar kinds of hornbills in the Philippines belonging to the genus Penelopides, but these species do not look exactly alike and live geographically apart.

Where does the Mindoro Tarictic live?

About a hundred years ago, the Mindoro Tarictic was abundantly found in lowland areas, and even during the 1970’s they have been reportedly seen in flocks of up to 50 individuals.

These numbers have been rapidly declining, and reports say it is now rare to see them in flocks of seven.

What makes survival difficult for these birds? First of all, the forest, their home, is shrinking. Everyday it gets smaller and smaller due to logging and land conversion for agriculture. Secondly, they are hunted for food. Because of their size and visibility, they are easy shooting targets. Now, the Mindoro Tarictic is sighted in a few lowland primary forests, forest edges, or secondary growth forests.

The Tarictics have also been seen in isolated woodlots and even in single fruiting trees in cultivated areas, but prefer closed canopy forests. They are rarely seen beyond 1,000 meters above sea level unless they are disturbed by human activities in the lowlands. Although they have been seen to feed in forest edges, hornbills by nature are arboreal and very dependent on large forest trees, living and feeding off the upperstorey or canopy of a forest.

The Mindoro Tarictic has been classified as an Endangered species by the International Union for the Conservation of Nature (IUCN). This means that it is at a very high risk of extinction, and unless something is done to save them, the Tarictics of Mindoro will be gone in the next 20 years.
Besides their aesthetic value and their right to life, Tarictics play an important role in forest regeneration as they disperse the seeds of the fruit trees that they feed on. They are part of the intricate web of forest life, from which our human needs such as water, food and shelter can be traced back to.

Several groups in Panay and Negros Islands have worked over the years to be able to save their Tarictics. There are existing facilities for rescue and captive breeding, and ongoing research on how to stabilize the population of the Visayan Tarictics. Unfortunately, there have not been the same conservation efforts specific for its kin in Mindoro.

A tarictic feeding tree

What is life like for this bird?

Mindoro Tarictics forage for food either alone or in groups, and sometimes even with other birds such as the Green Imperial-pigeon and the Coleto. Usually there is a lookout among the group who will first scout the area for predators before the rest of the group perches on the food tree.

Its diet includes carbohydrate-rich figs, lipid-rich drupes and capsules and other watery fruits. These include fruits of the Balete, Dao, Is-is, Igyo, Malugai, Kalumpit, Tuai, and Duguan trees. An insect or small animal may occasionally spice up its meal. It is fascinating to watch hornbills eat, as they peck at the food, place this at the tip of their bills, then toss it before swallowing. If the food bit is too big to swallow, they will chew on this, place it again at the tip of their bill, then toss back to their throat.

Unlike other birds, the nest of a hornbill is a cozy cavity high up in the trunk of a large tree. Biologists believe they breed around the months of April and May.

It is sad to note that when a foraging male Tarictic is caught or killed, its female partner also dies of starvation. The females do not leave their nestholes during breeding season and are highly dependent on their male partners to bring home food. Biologists also observe that fidelity is a trait among Tarictics.

What can be done?

The greatest threats to the flying foxes are habitat loss, disturbance of roosting area, and hunting for food and for trade. Air guns, shotguns, slingshots, thorny vines, nets and tree snares are used to catch them, but the most destructive of these are nets, since juveniles and those in pregnancy get caught as well. Statistics estimate that a seasoned hunter can bag as many as 50 flying foxes per month!

Studies such as population counts and monitoring have been effective at estimating remaining numbers and rate of decline of this species. However, more research is urgently needed if we are to stop the extinction of flying foxes. There is still very little known information about their habitat, foraging range, roosting behavior, diet and natural history. Researches on this would greatly help conservationists assess how the species can be saved.

Marks and colors of a Mindoro Tarictic

• Head, neck and underparts - yellowish white
• Ear coverts and band across throat - black
• Upperparts, upper tail-coverts and wings - black with metallic green sheen
• Tail - brick red with black tips
• Bill - wide and hooked (casque), black with yellow tip and yellow stripes across upper mandible (stripes become more developed with age)
• Eyes - reddish brown
• Legs and feet - dark brown
  

Artwork by Oscar M. Figuracion
Photo of tarictic feeding tree by Jennifer Dimas
Photo of captured tarictic by Michael Edrial

Flying Foxes of the Philippines

A Flying Fox?

The Philippines indeed, has flying foxes, but they are not actually foxes that have wings. Flying foxes are actually bats that look more like miniature dogs with wings.

They belong to the order Chiroptera and the family Pteropodidae. There are nine known species of flying foxes in the Philippines, and one that is believed to be already extinct.

The smallest flying fox

Very little is yet known about this particular flying fox, but it can be presumed that its population is very small, and that the species is probably highly endangered.

It is small and slim with sharp and sleek facial features, has mottled wings and is covered by brown downy fur. Mature males tend to have darker fur and wings than the sub-adults and juveniles, which have light-medium grayish brown and finer fur.

The Mindoro Pallid Flying Fox (Pteropus sp. A) is yet undescribed, but it could possibly be the smallest flying fox in the Philippines. It has been found in Mindoro, in the Anahawin River in Mts. Iglit-Baco National Park, and also in the lowland forest of Tandakan, Mt. Siburan in Sablayan, an area made up of drastic and gradual slopes with riverines in between, near a kaingin area, and in bamboo vegetation. All areas were predominated by trees of the family Dipterocapaceae.

Habitat

Flying foxes are active species, perching on tall trees in lowland forests. They live as a colony and gather in trees, called roosts. They normally sleep during the daytime unless disturbed, and go out to forage at night.

They feed on fruits of forest trees, and are even known to eat fruits from our backyards and plantations!

As fruit eaters, flying foxes are important dispersers of seeds, pollinators, and facilitators of gene flow of vegetation between island ecosystems. The extended time that seeds are retained in their stomachs aids long distance dispersal, which greatly contributes to forest regeneration.

Threats

The greatest threats to the flying foxes are habitat loss, disturbance of roosting area, and hunting for food and for trade. Air guns, shotguns, slingshots, thorny vines, nets and tree snares are used to catch them, but the most destructive of these are nets, since juveniles and those in pregnancy get caught as well.

Statistics estimate that a seasoned hunter can bag as many as 50 flying foxes per month! Studies such as population counts and monitoring have been effective at estimating remaining numbers and rate of decline.

However, more research is urgently needed if we are to stop the extinction of flying foxes. There is still very little known about their habitat, foraging range, roosting behavior, diet and natural history. Information on this would greatly help conservationists assess how the species can be saved.

The real name of the Flying Lemur is Colugo (Cynocephalus volans). The Colugo is a nocturnal mammal and not related to the Lemur and actually not able to fly. The colugo is slender, long limbed, large clawed, and long tailed, with a foxlike head and has soft, mottled fur.A large, furred gliding membrane is attached to the neck and sides of the body and extends along the limbs to the tips of the toes and tail. It allows the animals parachute - style glides from tree to tree. The animal is almost completely arboreal and is a slow, skillful climber. On the ground it is slow moving and nearly helpless. During the day it hangs by its claws in secluded branches or rests in hollow trees; it is most active at twilight and early dawn. The colugo feeds on leaves, flowers, buds, and fruit.

The malay Civet - cat (Viverra tangalunga) is the best known among the civets. Civets play an important role in spreading seeds in the forest over long distances. They have a long body about the size of a domestic cat, short legs, a tapered head with small ears, and a long, bushy tail. Generally they are yellowish-tan or grayish, with patterns of black spots or stripes or both. They are nocturnal hunters that prey on small animals, but they may also eat carrion and vegetable matter.

The Long - tailed Macaques or Crab - eating Macaque (Macaca fascicularis) is common all over South - Easte - Asia. They have a grey to brown - reddish fur. They raech 40 - 50 cm, the tailis up to 50 - 60 cm. Male animals reach 4,8 - 7 kg , females only 3 - 4 kg. They feed on fruits, crabs, flowers, insects, mushrooms and gras, but the main diet are fruits.

The Philippine Nectar Bat (Eonycteris robusta) is also endemic in the Philippines. Like the Golden Crown Flying Fox it also belongs to the fruit bats.They feed on nectar and old, overripe fruits. Also this species is highly endangered.

Aside from the asian or indian Cobra also the Kingcobra occurs on Samar. With 3,7 m the kingcobra is the largest, venomous snake in the world (the record is 5,58 m) and mainly feeds on other snakes. The asian cobra seldom reaches more than 1,8 m. To get bitten from a cobra is for humans always dangerous.

The endemic and highly endangered Philippine Cockatoo (Cacatua haematuropygia) is a small parrot. The animals live in large groups. Only in the mating season, couples stay alone. Often the same trees are used for breeding. Phil. Cockatoos feed on seeds, partly also on fruits, buts and flower

Unique amphibians and reptiles of Negros and Gigante Islands

Limestone karst habitats of amphibians and reptiles in southwestern Negros Island

Two species of forest frogs of the genus Platymantis (Family Ranidae) and one species of Gekko (Family Gekkonidae) have probably evolved in forested limestone karst formations in southwestern Negros Island and the Gigante Islands off northeast Panay Island. The caves and rock crevices in these karst formations must have provided a stable, favorable environment for evolutionary processes. Limestone karst formations in the Philippines, however, deserve more studies. It is hypothesized that the ancestral stock of Philippine Platymantis species came from islands south and southeast of the Philippines, and that of Gekko gigante came from either the south-southeast or southwest source areas since the genus Gekko is distributed in the Oriental-Australian region as well as in the eastern Palearctic region.

Two species of forest frogs (Family Ranidae), Platymantis spelaeus Brown & Alcala and P. insulatus Brown & Alcala, and one species of lizard (Family Gekkonidae), Gekko gigante Brown & Alcala were discovered in limestone karst forests of southwestern Negros Island and the Gigante Islands off the northeastern tip of Panay Island in the 1960s.

Limestone karst herpetofauna: A. Platymantis spelaeus in southwestern Negros Island, B. Platymantis insulatus in Gigante Islands, and C. Gekko gigante in Gigante Islands. Photos by A.C. Alcala and Jasper Maypa, SUAKCREM, 2004.

Based on current knowledge, of the seven species of Platymantis known from Negros and Panay, only these two species inhabit exclusively deep rock crevices and caves in limestone forests.

The other five species occupy various habitats in both limestone and non-limestone forests. Among the lizards of the genus Gekko, one species, G. gigante, inhabits only rock crevices and caves in the limestone forest and two other species (the Philippine endemic G. mindorensis and the non-endemic G. monarchus) are found in caves in limestone forests and in other habitats in non-limestone forests.

Limestone cliffs in Gigante North Island. Photos by SUAKCREM staff in April 2004.

The two frogs and the lizard we are concerned with utilize rock crevices and caves (entrance and part of twilight zones) as hiding places during most of the day but venture into the open at night to feed. They also use caves as egg-deposition sites. P. spelaeus lays large, yolk-rich eggs in moist (relative humidity, 90-100%), cool (temperatures, lower 20so C) rock crevices inside caves that develop directly into froglets. P. insulatus most probably also does so, like most (or all) other species of the genus Platymantis. Gekko gigante attaches its eggs to roofs or walls of caves.

Karst formations are characterized by the presence of limestone or other soluble rocks like dolomite and marble and by subterranean drainage resulting from the dissolving action of water on the bedrock. Karst topography is dominated by sinkholes, sinking streams, large springs and caves. Cool air in contact with ocean or underground streams may circulate in caves, bringing temperatures to levels lower than those above ground. Caves have therefore provided favorable habitats for the evolution of some animal species such as arthropods (e.g. crustaceans) in Hawaii and vertebrates (e.g. fish) in Mexico. Since P. spelaeus, P. insulatus and G. gigante are strictly confined to limestone karst habitats based on our extensive field observations, they most probably evolved there.

It appears that karst areas, which retain moisture for long periods of time, can confer protection to amphibians and reptiles, provided the forest cover remains intact. This is supported by the fact that two El Niño events in the 1980s and 1990s apparently did not negatively affect the populations of these three species, indicating good prospects for survival in the face of future climate changes. However, a long term study of amphibians and reptiles inhabiting rocks and caves in limestone forests is needed.

The origin of the ancestors of the three species may be related to the geology and geological history of Negros and Panay Islands. The limestone karst habitats of these three species are part of the Negros volcanic arc, dating back to the Miocene Epoch (between 5 and 24 million years before Present)

Eggs of Gekko gigante glued to roof of cave on Gigante South Island. Photo by Leonardo Averia.

Geological evidence supports the view that the islands of Negros, Panay, Cebu and Masbate formed one Ice-Age island mass when the sea level was 100-120 meters lower than the present level about 160,000 and 20,000 years ago during the Ice Age (Pleistocene Epoch)

The ancestral stock that gave rise to the Philippine platymantine frogs in the Philippines (present estimate of the number of Platymantis species 36-40) came from islands of the Southwest Pacific, south and southeast of the Philippines (Fig. 6). This happened during the Pliocene-Pleistocene Epochs 5-1.6 million years ago. As presently known, the distributional range of Platymantis species in the Philippines includes the Luzon, Mindanao, and Visayas Ice-Age islands as well as Mindoro, Sibuyan, Siquijor Islands. But these frogs are absent in the Palawan and the Sulu Ice Age islands

The ancestors of Gekko gigante may have colonized the Philippines in the same manner, but there is an alternative route through southwest Philippines, that is, from Borneo via the land-bridge Sunda island of Palawan and the Sulu Archipelago, the entry pathway of the ancestors of many Philippine herpetofaunal species.

A study in progress of other limestone karst formations in the Philippines may reveal findings similar to those reported in this paper.

Raffesia mira: yet another reason to be proud of the Philippines!

Rafflesia manillana ( Photo: Benito Tan, Vanishing Treasures of the Philippine Rain Forest by L. Heaney and J. C. Regalado, Jr.)

By Art Fuentes

A biologist once said that for every species named, there’s still another four or five waiting to be discovered.

Some people may see this remark as an article of faith rather than a statement of fact. But sometimes keeping faith has its rewards.

Another species of the rare giant flower Rafflesia was discovered here in the Philippines. Filipino scientists led by Dr. Edwino Fernando and Dr. Perry Ong trooped to a remote mountain in the town of Maragusan, Campostela Valley Province in Mindanao. They came to verify a story that was until then mere rumor—another species of the strange bloom was growing there.

It was true. The scientists, overcome perhaps with their own discovery, named the new plant Rafflesia mira.
Their discovery is made even more astonishing when considered that barely three years ago in 2002, another species of the extremely rare plant was found in the mountains of Antique province. Named Rafflesia speciosa, the rare flower has since been adopted as the official symbol of the Sibalom Natural Park and the municipality of Sibalom in Antique Province.

R. mira is the fourth Rafflesia species identified in the country, along with R. speciosa, and R. manillana. Another species, R. schadenbergiana was last recorded in 1882 in Mt. Apo in Davao. It has not been seen for more than a century and is now believed to be extinct.

If it is true that for every species named, there’s still another four waiting in line, then we really have barely scratched the surface, as shopworn as that may sound.

Rafflesia speciosa

Strange bloom
The Rafflesia is completely unlike any bloom you have ever seen, or for that matter will ever see. Unlike other flowers that are just parts of plants, the Rafflesia flower is the plant itself.

It also exists, without the usual parts we have come to associate with flowers, or even plants—no stem, no branch, not even leaves. But its real strangeness lies in its size, these blooms range in diameter from a cabbage head to a car tire. Finally, instead of the pleasant scents we’ve come to normally identify with flowers, most of these giant blooms emit a foul rotting odor.

Rarest of the rare
The flower is named after its European discoverer Thomas Stamford Raffles. First discovered in Sumatra in 1818, more than twenty Rafflesia species have been found so far in different parts of Southeast Asia. Many of the species are extremely rare, and have been recorded from only a handful of localities.

The flower is actually a parasite. It grows within its host, the tetrastigma vine, and in its early stages appears as but a tangle of fibers. It only starts manifesting itself during its reproductive cycle. Outgrowths appear on the root vine (1), then cabbage-like buds develop (2), then a fully open flower blooms (3) and bears fruit. The flowers themselves take a long time to develop.

From the time the bud appears, it can take 9-10 months for the flower to bloom. Not all buds bloom into flowers, a lot of buds decay before they can even open. Too much rain causes the buds to rot, while too little rain causes them to shrivel up and dry.

Lifecycle
Each flower is either male or female. Female flowers are rare, and of these, fewer still are fertilized. The flowering episode itself is brief, and will last no more than a couple of days. Once in bloom, the flower releases a putrid scent that attracts flies and other insects that serve to pollinate it. For a female flower to get pollinated, a male flower must be nearby and also in bloom.

1	2	3	4
Photo: Manila Bulletin

After a period of 3-5 days, whether or not they are successful at pollination, the flowers begin to wither and turn black. If the female flower was successfully pollinated, it will bear fruits that get buried somewhere near the bottom, waiting to be picked up by forest rats, insects or other animals. Finally, for the seeds to form another bloom, they need to find their way to the right kind of vine.

R. mira, a remarkable and surprising discovery.

Rafflesia mira (Fernando and Ong sp. nov.) in Mt. Candalaga, Campostela Valley Province, Mindanao.Reprinted from Asia Life Sciences G14(2):269, 2005. Photo by Rhonsan Ng
New discovery What could possibly be the smallest of the largest species of Rafflesia in the Philippines was recently discovered in Mt. Asog in Camarines Sur. It measures 12-13 cm in diameter. The discoverer, a group of researchers from the Camarines Sur State Agricultural College, proposed that the species be named Rafflesia irigaenses. (Photo courtesy of CSSAC)