Paper on Sulu endemic avifauna published

Updated: Aug 6, 2020

van de Ven et al 2019

Birds, and in fact all terrestrial wildlife in the Sulu Archipelago are severely threatened. The simple fact is that the area is very very small. It is, however, one of the six main biogeographic regions for biodiversity in the country. This area has been relatively understudied, as it is remote and the political situation has always been difficult. The islands host no less than six species of birds that can be found nowhere else in the world; the Sulu Hornbill Anthracoceros montani, Sulu Bleeding-heart Gallicolumba menagei, Sulu Hawk-Owl Ninox reyi, Sulu Pygmy Woodpecker Dendrocopos ramsayi, Blue-winged Racket-tail Prioniturus verticalis and Tawitawi Brown Dove Phapitreron cinereiceps. Unfortunately, all six are recognized, both by the IUCN as well as the DENR, to be threatened with extinction. Three of them even critically so. When Nikki Dyanne was invited to present at the National Conference for Environmental Science (NCES) in Bongao, this was a good opportunity to dive deeper into the subject, and hopefully create more awareness and generate more attention to the plight of the birds.

The Sulu Archipelago

The Tawi-Tawi College of Technology and Oceanography (TCTO) is the local branch of the Mindanao State University, and located in Bongao, Tawi-Tawi. As the name already implies, the institute is geared mainly towards Oceanography. Not surprising, as by far most people living on the islands rely on the sea for their livelihoods in one way or another. From a biological standpoint however, the seas around Tawi-Tawi are very similar to those around other islands in the Philippines and South-east Asia. They are, after all, connected to each other. The land area is a different story. The islands of the Sulu Archipelago are volcanic, and have never ever been connected directly to any other land masses. During the last ice age, some 12.000-15.000 years ago, when global water levels were up to 150 meters lower than today, some of the islands of Sulu were connected to each other, but never to the mainlands of what we now call Mindanao or Borneo. Thus, the terrestrial ecosystems have been able to develop independently for a long time. As seen in the other bioregions of the Philippines, this stimulates speciation, and indeed a number of species split off from their relatives on other islands and became endemic to the area. A lot of very interesting topics for anyone from MSU-TCTO studying biology.

What DO we know about Sulu endemic avifauna?

So if there are so few people studying these species, and the islands are so difficult to access, do we even know for sure that these birds are threatened? This is the question that motivated us to dive deeper into the literature, to find out what do we really know of these birds, and what needs to be studied. Nikki, together with Willem and Richard Muallil of MSU-TCTO, reviewed all available sources of materials about bird surveys on the islands and compiled them in the paper that was just recently published in the special issue of the Philippine Environmental Science Association (PESA). A link to the journal can be found HERE. Our paper is also attached HERE and can be freely downloaded.

Sulu Hornbill

First meeting of the Sulu Hornbill Recovery Group

When Nikki presented at the NCES conference in 2016, the debate and conservation actions were again starting up, generating more interest for this species. We had recently organized a workshop specifically for Sulu Hornbill conservation opportunities, and gotten a grant to do more studies on the islands of Tawi-Tawi and Sanga-Sanga. The Sulu Hornbill Anthracoceros montani is listed as Critically Endangered (IUCN and DENR) with reportedly only around 30 individuals left in the wild. None exist in captivity as far as we are aware. As a large and relatively noisy bird, they are quite easy to detect. It is therefore assumed they are now extirpated on the islands of Jolo as well as Sanga-Sanga, and remain only on Tawi-Tawi and perhaps on nearby islands. Although the official accounts do not mention this, we found surveys in the grey literature that indicate that they did/perhaps do occur on offshore islands in Tandubas.

The attached map gives an indication of where surveys have been done before. It can be seen that all of these are coastal locations. As far as we could determine, no one has ever been deep inside the forests on Tandubas or between the municipalities of Languyan and Panglima Sugala. Only the islands of Bongao and Sanga-Sanga, now mostly deforested, and the western part of Panglima Sugala have often been visited. The estimate of 30 individuals stems from these very few localities. The habitat in the unsurveyed areas, however, seems to be quite suitable for this species. Although little is known about its ecology, Sulu Hornbills is of the family Anthracoceros. Other species of this family are the Palawan Hornbill A. Marchei, the Oriental Pied Hornbill A. albirostris and the Black Hornbill A. malayanus. All of these are relatively easy hornbills, living in degraded forest and in the case of the Oriental Pied Hornbill, even in urban areas. This indicates that the habitat requirements for this species are likely to be less demanding compared to for example Rufous Hornbill (Buceros hydrocorax) or the Writhed Hornbill (Rhabdotorrhinus leucocephalus) which are primary forest obligates.

'Tausi' by Romar Lintag

With the habitat suitability of the remaining parts of the island, I am of the opinion that there are quite a few more Sulu Hornbills still roaming the island. Although this would increase the hope for survival of the species, they will nevertheless remain Critically Endangered for a long time, as even 300 individuals would be alarmingly low for any population.

Nevertheless, there is still hope for this species, as long as there are people fighting for its survival.

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