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Search for a Philippine eagle Family at the Mt. Apo Geothermal Reservation

Juvenile Philippine eagle hunting a macaque

The Philippine Eagle Foundation (PEF) endeavors to find all eagle nesting sites within the Mt Apo Key Biodiversity Area (KBA) and help protect each of these nest sites. Philippine eagle nest sites are ANCIENT breeding areas – generations of eagle pairs have occupied the same nest site over and over again. Conserving these core areas of reproduction and keeping the nesting pair and their young safe is pivotal to the success of saving the species from being lost forever.

In 2019, the PEF, Energy Development Corporation (EDC), and the Department of Environment and Natural Resources (DENR) launched a project in “Search for the King of Birds” along the western slopes of Mt Apo. We began the search at the Mt Apo Geothermal Reservation in Kidapawan City where eagles were seen in the past. Apart from enhancing local awareness about and capacity for eagle conservation, another project objective is to find and study an eagle pair and their active nest within or around the reservation.

Two expeditions in 2019, one in July and another in September, found one Philippine eagle close to the reservation. The bird is suspected to be immature, perhaps over 3 years old, and thus is a floater (sexually immature and unpaired eagle). The presence of an immature eagle indicates that its eagle parents could be nearby.

In compliance with COVID-19 protocols, the PEF Team (Senior Biologist Ron Taraya and Field Intern Keanu Sitjar) underwent a mandatory 14-day quarantine at a hotel in Kidapawan City. They also had an RT-PCR test, and went through other medical screening procedures. After getting cleared of the virus and passing other tests, the team, together with EDC Forest Aides Climclim Lumayon and Renjie Sinding, embarked on the month-long expedition in November.

We focused our eagle search on the forests where a lone Philippine eagle was detected in July and September of 2019. The terrain at the survey site was very steep, and the forest vegetation is lush. With binoculars and field telescopes, the team alternately occupied four observation posts (OP): three on the ground and one on an elevated platform. The fourth OP set up on an elevated platform gave the team the closest view of the gorge and its surrounding forests.

After spending 192 observation hours deep in the forest finding and documenting Philippine eagles and other raptors in frequent rains, the team managed to detect one eagle pair and their 2-year-old young.

There were at least eight instances that Philippine eagles were documented or a total contact time of 1,590 minutes or 26.5 hours. That is binge watching 30 episodes of the Game of Thrones! Those exhilarating moments of watching the family of eagles comprise only 14.0 % of the 192 observation hours of the entire expedition.

Confirming a Philippine eagle couple

It was on November 4 when we finally saw our first Philippine Eagle. Around 1052, while scanning the tree lines, our adrenalin surged upon seeing an eagle perched inside the canopy above a waterfalls. At 1109 hr, the bird took off and flew in circles above the falls. As it was about to head towards the other hill, another eagle appeared and started “chasing” the other eagle. Our hearts raced at the sight of the eagles doing their elegant aerial rituals.

The eagle couple then began what appears to be a courtship routine. The two eagles mutually presented their talons in mid-air called “talon presentation”. They also did several bouts of flying together in spirals or “mutual soaring”. Then they flew to different directions; one disappearing inside the deep gorge, while the other landed on an emergent tree. There, the eagle stayed on its perch cleaning its feathers with its beak called preening. It was also seen scratching, stretching, and moving its head. After performing these general maintenance behaviors, the eagle finally flew off and glided beyond the waterfalls until it disappeared behind the tree line at 1316 hr.

We could hear our hearts pumping as we witnessed an unmistakable breeding behaviour of two mature eagles. In Mindanao, September 2020 to January 2021 is the nesting season for Philippine eagles, and courtship displays precede each egg-laying. Eagle pairs at several nests sites of Mindanao start their courtship rituals above their nesting area as early as July, but the routine can last even until the pair is already rearing a chick. These observations strongly suggest that the forest we investigated is a new Philippine eagle nesting territory at the Mt. Apo KBA.

Documenting a juvenile Philippine Eagle

On November 5 occupying OP 2, we were eager to see “prey delivery” and/or “sprig delivery” behaviours that would lead us to a possible nest tree. To the group’s great delight, two eagles were spotted again at 0915 hr. The eagles glided steadily on level cruise, with one trailing the other. They emerged from the same spot where one of the eagles disappeared the day before. One eagle landed on a tree that is visible to the group, while the other rested on a concealed spot.

We were carefully taking notes of the eagle’s behaviour through our fieldscopes when we heard loud, crying calls from another eagle. The calls were typical of “food-begs” from a very hungry young eagle. Food-begging calls are mostly exhibited by juveniles whenever an attending parent is nearby. The hungrier the eaglet, the louder its calls get. The calls were heard many times, between 1025 to 1128 hrs. The rains started pouring at 1300 hr and the calls also stopped.

The team occupied the post early the following day in anticipation of another eagle encounter. And at exactly 0838 hr, loud eagle calls were heard once again. The “food-begs” echoed across the forests and it took us a while to find the eagle. Finally, the eagle emerged on a tree directly above the falls, and called loudly every after 5 to 0 minutes.

The bird was over a km from our post, and at that distance, it was very difficult to see the bird’s physical features in detail. One can tell whether a bird is juvenile or adult based on the shape of its feathers, the colour of its legs, and its general appearance. The bird calls resemble infantile vocals, but we wanted to have a closer look to be sure. An adult delivering food and feeding the eagle is another proof that the bird is a juvenile.

Our prayers were answered. An adult eagle appeared above the ravine at exactly 1213 hr and flew towards the direction of the calling bird. And to our great excitement, the bird is carrying a freshly killed prey. The “food begs” intensified as the other eagle flew above the ravine.

At 1250 hr, the two eagles were now in one tree, and at 1314 hr, the calling bird started feeding on the prey item that the other eagle left. The team jumped with joy after confirming that indeed, the loud bird is a juvenile eagle. Around 1339, another eagle soared above the feeding tree, and disappeared behind the hills. The eagle ate until 1420 hr, and then flew and hid amongst the vegetation.

The team went out at 530 hr on Nov 7. This time, we were motivated to check whether the tree, where the adult eagle dropped the food and the juvenile ate its food ration on, is a nesting tree. From afar, the feeding branch looked like a huge nest bowl. We also wanted to know if the juvenile spent the night at that particular tree.

And we were right; the eaglet indeed slept there. The team saw the eagle at 0624 hr on the same feeding branch it used. It was sun-bathing, drying its feathers using the hot rays of the early morning sun. And for over 8 hours, the bird stayed on the same tree. During the course of the day, we saw it perform general maintenance behaviours, but most of it were “food begs”.

During one of these food-begs, at 1306 hr, the immature bird did quick, wing flapping movements while calling towards something in the forests. Such behaviour is typically done by juveniles when an attending adult is nearby. But we didn’t see any eagle until 1432 hr. The eagle parent landed on a different tree, and left eventually at 1501. It flew above the tree where the young eagle was perched and calling vigorously, and disappeared behind the tree line. The juvenile eagle trailed its parent’s flight path and also disappeared behind the forests. Then, the eagles were not seen for days.

To know for certain if the tree is a nesting tree, the team decided to find a closer observation post at the forest edge on November 12. From OP 1, the team hiked down the ravine, crossed a river, and hiked up a plateau. We broke up into two teams: one team was assigned to occupy OP 3 and observe for eagles, while the other team hiked and went closer to the suspected nest tree.

But close inspection of the tree showed that it does not qualify as a suitable nesting tree. It did not have the typical nest bowl, and the associated thick ferns and other epiphytes that one will find in an old nest. It appears that the tree is more a “feeding tree” than a nesting tree. We did not see a single eagle, but we were still fired out to get a closer view of the eaglet and estimate its age. The team was motivated in finding the best observation post possible that is close to the feeding tree, and the places where the adult eagles and the juvenile stayed during the previous days.

On November 13, we established OP4 – an elevated platform that gave us a good view of the whole forests. The following day, we occupied our new platform and waited. And at 1314 hr, two Philippine eagles were again spotted circling just above the ridge. But the mutual soaring did not last a minute, and only one Philippine eagle landed on a spot that is visible to us. The other eagle, which we suspect is the juvenile, hid behind the foliage. We heard it calling, but never saw it for the rest of the day.

Driven by the opportunity to see and photograph the eagles up close, the team made the grind of walking for 3 hours each day to and from OP 4. We hiked through two gorges, across a river, and through the plateau for the next four days for that opportunity. But not a single eagle soul was seen in those four days.

Finally, our perseverance paid off. Last November 19, at exactly 1146 hr, the juvenile Philippine eagle soared just above OP 4. Using our DSLR Camera and zoom lens, we took as many photos of the juvenile as possible as it circled above the forests and nearby farmlands close to our post for about four minutes. It then landed on an emergent tree and defecated. Now closer to the bird, about 200-300 m, the relatively sword-tipped flight and tail feathers of the juvenile eagle were visible. The bird also had all the other features typical of a 2-year-old juvenile such as awkward hunting moves, lower flight confidence, and limited flight duration.

And the juvenile showed off even more. It amused us watching the bird take on a group of long-tailed macaques Macaca fascicularis foraging on an escarpment just in front of the waterfalls.

At 1330 hr, the juvenile already had its eye on the foraging macaque troop across the valley. Until finally, it leaped and darted towards the troop. This caused the macaques to run frantically in different directions to avoid the lethal claws of the immature bird. As a desperate move to corner a macaque, the bird tried to balance on a bush close to the ledge and squeezed its body through the vegetation. But the poor bird could not get through because of the thick foliage resulting to the macaque’s easy escape.

And then, the macaque alpha male and its comrades faced off with the bird and gave off threat grunts and alarm calls. The bluff worked, and the bird backed off, and retreated to a tree above the ledge. At 1429 hrs, the young eagle issued a series of infantile vocals, until it flew off, circled, and disappeared behind the falls. The juvenile eagle was seen again on November 20 and 23 around the cliff where it attempted to hunt the macaques.

We have confirmed a new nesting territory, with its resident eagle pair and a young eagle on its post-fledging stage. Based on the general appearance of the juvenile eagle, its behaviour, and the behaviour of its attending adult parents towards the bird, we estimate that the age of the young eagle is 2 years old. Following the eagle’s nesting cycle on Mindanao, the eagle pair could be laying an egg soon.

Other Raptors

Aside from detecting the “critically endangered” Philippine eagle, there were seven other raptors seen during the expedition. These raptors are the Philippine Serpent Eagle (Spilornis holospilus), Philippine Honey buzzard (Pernis steerei), Brahminy Kite (Haliastur indus), Philippine Falconet (Microhierax erythrogenys), Chinese sparrowhawk (Accipiter soloensis), The crested honey buzzard ( Pernis ptilorhynchus), and the Peregrine falcon (Falco peregrinus).


Article by Ron Taraya and Jayson Ibanez, PEF

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