This article is based on a presentation made by Alex Tiongco and Marts Cervero at the 7th ARRCN Symposium held in South Korea in January 2012. Delegates from countries along the Asian Continental and Oceanic flyways from as far north as Mongolia and east as India attended the symposium. There were also delegates from the UK and USA who tooK part. The Philippines was asked to host the 10th Symposium in 2018.
RAPTOR MIGRATION IN THE PHILIPPINES: AN OVERVIEW
by Alex Tiongco and Marts Cervero
East Asia has two major Raptor Migration flyways:
1) The Continental – This flyway is mostly over land which encompasses the breeding areas on Northeastern Asia and stretches down to mainland Southeast Asia; Thailand, Peninsular Malaysia, then on to Sumatra, Bali, and the various Indonesian Islands, a branch goes up to Borneo and on to Mindanao and Palawan(?). 25 species of raptors are known to pass through the Isthmus of Kra a few miles north of the border between Thailand and Malaysia.
2) The Oceanic – This flyway is fraught with vast ocean crossings covering the breeding grounds on Northeastern Asia, to Taiwan, the Philippines and on to Borneo and other islands of Indonesia.
It is estimated that more raptors by far utilize the shorter Oceanic route rather than the much longer Continental route. Generally the ones using the continental route are the much heftier raptors like eagles which are adverse to crossing large expanses of seas, whilst more of the smaller accipiters use the Oceanic route. It should be noteworthy that during the spring migration of 2007 about 230,000 raptors were seen over Sangihe, mostly Chinese Goshawks.
Status of Raptowatch in countries on the Oceanic flyway
Extensive studies of Raptor Migration are being conducted by Japan, Korea and Taiwan and the knowledge ends there. Indonesia has been long involved in raptor conservation and migration projects of the ARRCN but because of the vastness of her area, a great deal of information still needs to be discovered.
No structured studies and counts have ever been conducted in the Philippines which presents a substantial gap in the study of the Oceanic migration routes, of species and numbers of migrants on passage and of their ecology in our vastly unstudied wintering ground.
Comparison of species of Migratory Raptors found in Taiwan, Philippines, Borneo and Indonesia
Taiwan reports 14 regularly occurring species of migratory raptors compared to which the Philippines has13 species. Taiwan considers Black-shouldered Kites to be migrants whilst we consider them to be residents. Taiwan does not consider Pied Harrier and Merlin to be regular migrants (accidentals?). Merlin is likewise considered accidental to the Philippines and since we have breeding populations of Pied Harriers we consider them to be both resident and migratory. We have yet to spot the following Migratory Raptors from Taiwan: Eurasian Sparrowhawk and Northern Goshawk.
So far, on Sangihe, Indonesia, only 6 species of Migratory raptors have been reported: Osprey, Harrier sp. Chinese and Japanese Sparrowhawks, Grey-faced Buzzard and Peregrine Falcon. Absent from these Islands are the Oriental Honey Buzzards which are regularly reported on Mindanao.
We are still unable to obtain information on the number and species of migratory raptors coming from the Philippines to North Borneo either through Palawan or Zamboanga. Borneo however is unique as it is established that Raptors using the Continental route are known to go up to Borneo and some go on to Mindanao, and Palawan(?).
Position of the Philippines in the Oceanic route
The Philippines is located at approximate positions from 4 degrees 12” to 21 degrees 30” North and from 112 degrees 30” to 122 degrees East. Longitudinally, it is about 1,000 miles and it has a breadth of about 840 miles. A raptor with an average speed flight of about 35 miles an hour would take over 28 hours to traverse the whole length of the archipelago.
Raptors are relatively hefty (in bird dimensions) and are built for relatively short bursts of flights. The Philippines should therefore necessarily be Migratory Raptors’ rest stop (if not their wintering ground) on their way to their wintering grounds in Indonesia. The Chinese Sparrowhawks which are purely passing migrants in Pen Malaysia and North Borneo are known to winter in the Philippines.
If you imagine the Oceanic Migration route to be an hour glass, Taiwan and Luzon serve as the neck (a choke point) of the hour glass. It is believed that from Luzon, the Oceanic flyway branches out to various tributaries. It is believed that some raptors go to Borneo through Palawan, others to go down to Zamboanga and are believed to go on to Borneo, still much more go to Davao and perhaps on to the small islands of Indonesia – Sangihe and Talaud(?) and onwards to the wintering grounds in Indonesia.
Unlike Korea or Taiwan, the Philippines is not a chunk of land but rather a long archipelago consisting of a chain of over 7,100 islands, each major island a microcosm in itself, with many remote nooks and crannies making a cohesive and comprehensive study of raptor migration seemingly quite formidable.
On the other hand, it provides a great array of places to concentrate on. The Northern tip of Luzon and southern tip of Davao would be a good areas to study where raptors from Taiwan and Indonesia respectively, make their landfalls and vice versa, where they leave from on their way to these places — which is absolutely necessary in order to protect and preserve the habitat which these exhausted migrants use as a rest and roost point before and after a long sea crossing.
The north eastern tip of Luzon could tell us whether or not raptors do fly direct to and from the Ryukyu Islands to Luzon bypassing Taiwan – a hypothesis which has remained a mystery, despite sophisticated tracking devices employed by both Taiwan and Japan.
Palawan and Zamboanga are good places for coordination with North Borneo on the possibility of finding whether or not circular routes are taken by raptors which could be using both the Continental and Oceanic flyways.
The fields of study are endless.
Some statistics on distances and climate
1) Between the southern most tip of Taiwan and the northern most tip of Luzon is about 210 nautical miles so a raptor flying at about 35 miles an hour could cover the distance in about 6 hours, provided they do not do hops on the intervening islands – which they reputably do during inclement weather.
2) The distance between the northern most part of the Philippines and our watch area in Tanay is about 300 miles and flying straight from the northern land fall would take 8 hours approximately.
3) Between Mati, Davao to the Talaud Islands in Indonesia is 150 miles which is about 4 hours flight. There have been reports from locals of small accipiters flying in flocks during spring migration on Mati.
4) Between Batulak, Davao to Sangihe Islands in Indonesia is 120 miles or about 3.5 hours flight.
5) Beween Batangas to Mindoro is between 10 to 20 miles of sea crossing, Mindoro to Busuanga is 70 miles of sea crossing. The whole length of Palawan island is about 150 miles.
6) Between Zamboanga and Basilan is 15 miles of sea crossing, Jolo to Tawi-tawi is 60 miles, Tawi-Tawi to Dent Haven in North Borneo is 60 miles.
What is the importance of showing distances and flight times? This might indicate to us later on, the exact date and time to set up the watch in a given area of interest.
The Philippines is affected by 2 weather systems:
- The Northeast Monsoon which occurs from September/October to March/April of each year,
- Southwest Monsoon which occurs from March/April to September/ October of each year.
It seems that raptors start to move during the turn of the monsoon seasons.
Raptors in the Philippines
30 Diurnal Raptors:
- 4 endemic raptors, 6 if we accept that the Pernis celebensis in the Philippines is now Pernis steeri and if we split the Spizaetus Philipenesis into S p and S pinskeri
- 11 Resident Species,
- 9 purely migrant species and
- 4 both resident and migrant population for a total of 30 species.
Note: We have a report of a juvenile Cinereous Vulture found in Batanes in 2004 which died in captivity. Only juvenile Cinereous Vultures do short migrations from their breeding places in Mongolia. Juvenile Cinereous Vultures have also been reported in Taiwan as accidentals.
14 Nocturnal Raptors:
- 8 are endemic,
- 4 are resident and
- 1 completely migrant (Short-eared Owl – Asio flameus )
- 1 both migrant and resident population.
9 Migrant Species
Black Kite Milvus migrans
- The Kennedy book reports this to be accidental on Palawan
- Sighted in December 1907 but WBCP records have shown that there were sightings in May 2004 and June 2006 and 2007 and January 2009 in Cavite, Luzon. In July 2007 one individual was reported in Negros. Last year, 1 individual was reported during spring migration entering Taiwan from the south (Philippines?)
Eastern Marsh Harrier Circus spilonotus
- Kennedy reports this to be occurring from November to April in Luzon, Leyte, Palawan and Mindanao
- Club records show that this species was spotted in August 2006 in Southern Luzon
Japanese Sparrowhawk Accipiter gularis
- Kennedy reports this to occur in Luzon, Palawan and Mindanao from October to April.
- Club records show them to be present as late as 9 May on Luzon and as early as 22nd September on Mindanao.
Chinese Goshawk Accipiter soloensis
- This raptor occurs from August to May in almost all parts of the Philippines except Samar and small islands in the Visayas They are believed to winter in the Philippines. We have records of 2 sighting in 26th December 2006 at Cavite and 10th December 09 at Subic. In Pen Malaysia and North Borneo, which are in lower latitudes than the Philippines, they are known to be passing migrants. More studies are required on the matter of whether or not they really winter in the Philippines and if they are passing migrants on north Borneo.
Grey-faced Buzzard Butastur indicus
- These are found spread all over the archipelago from August to May.
Common Buzzard Buteo buteo
- These migrants are found in mountain forests of Luzon at 1000 meters. In other places like Korea and Malaysia these are found even on the lowlands.
Eurasian Kestrel Falco tinnunculus
- There are significant sightings of these raptors in the city during migratory time. They occur on Luzon, Palawan and Mindanao.
Eurasian Hobby Falco subboteo
- This is not listed in Kennedy but Club records show them to occur in the Philippines. In April 2004 there were 2 individuals migrating north over Tanay, Luzon; October 2004 one individual over Tawi- Tawi. There are also undocumented reports of sightings by Tim Fisher in Palawan and Batanes.
Merlin Falco columbarius
- This Raptor is reported to occur only in Luzon but the Club has no record of sighting this one
4 Resident and Migrant population
Osprey Pandion haliaetus
- This Raptor is listed as purely migratory in Kennedy and said to occur on Luzon, Mindoro, Palawan, Negros and Mindanao.
- However, Club records show that sightings are made all throughout the year. In June 2007 at Negros, 2 fledgelings were observed being fed by an adult. Close to Ipo Dam on Luzon, nesting behaviour is being observed with the bird carrying small sticks in flight. Club records also show them to be found elsewhere like Cebu, Antique, Samar, and Batanes.
Oriental Honey-buzzard Pernis ptilorhynchus
- This bird is seen throughout the year all over the Philippines except some small islands in the Visayas but the Club does not have sightings for June. This is very often confused with the resident Hawk-eagles and Barred Honey-buzzard Pernis celebensis which is being split into Pernis Steerii.
- The Philippines has 3 resident races – philippensis, orientalis and the palawanensis This is the raptor that gets new birdwatchers interested in Raptor watching especially during the Spring migration because if it happens to be there, they are seen in large numbers majestically flying low.
Pied Harrier Circus melanoleucos
- This raptor occurs the whole year round and is confirmed to breed also in the Philippines. It is found all over the Philippines except Ticao, Samar and Cebu, and Palawan.
Perigrine Falcon Falco peregrinus
- This is the most common raptor seen in the city. The local population is the subspecies ernesti. Both the subspecies calidus and japonicus which are transmigrant are also found in the Philippines. They occur in Luzon, Panay, Negros and Palawan.