BULLETIN OF THE BIOGEOGRAPHICAL SOCIETY OF JAPAN

BIOGEOGRAPHICAL SOCIETY OF JAPAN

Vol. 0, No. 18 H till 3® J|l ## September 193G

ON THE GUILLEMARD* ZOOGEOGRAPHICAL LINE

Marquess IIaciiisuka Ph.D.

British Museum (Natural History)

One of the best known zoogeographies! lines in the Philippine archipelago is that which separates and the archi¬ pelago. Sibutu passage has received considerable attention and many authors agree as to its importance. Dr. P. II. II. Guillemard first called attention to it and writes: "The is not zoogeographically separable from the . Westwards of the Island of Tawi Tawi the narrow Sibutu channel forms a boundary line between the archipelago and the greatly differing Borneo almost as striking as that shown by Wallace to exist between Bali and Lombok." "In Sulu", says Mr. P. W. Burbridge, a well-known botanist and explorer of the Sulu region, "the flora shows a marked resem¬ blance to that of the Philippines and the Celebes group." Everett, in Ibis, Volume VT, page 240, 1894, on the basis of

* Guillemard was a flue naturalist and explorer of Cambridge, best remembered through his book "The Cruise of the Marchesa to Kamsehailc.a ami New Guinea." First Ed. 188G; Second Ed. 1889; who showed great interest in the progress of my book "The Birds of the Philippine Islands," (Vol. Ill, under preparation). While I was exploring Central Africa he read several hundred pages of proof sheets in his Victorian styled house, under the light of an oil lamp. Guillemard and I remained close friends some ten years, until in 1933 death occurred in his 81st year. Original from and digitized by National University of Singapore Libraries Vol. (1 184 BULLETIN OF THE BIOOEOGRAPIIICAL SOCIETY OF JAPAN

his own observations 011 the distribution of avifauna as well as oceanographical report made by Captain Field of II. M. S. Egeria, supports Guillemard's view. He writes as follows: "From the day that I landed until 1 had to leave owing to no rice being procurable, I was unable to do any collecting or even to walk most of the time. Nevertheless my men worked well, and the collection is quite suf¬ ficient to show that the avifauna of the fawi-Tawi Islands is to all intents and purposes identical with that of the Sulu archipelago, the Philippine element immensely preponderating over that derived from Borneo even in Sibutu, although in the latter the Bornean infusion is more clearly discernible. You will recollect with regard to Sibutu that Guillemard, in the paper read in 1885 (P.Z.S. 1885, p. 247) on his Sulu collection, anticipated that 'a more extended knowledge of its avifauna would probably show a preponderance of western rather than eastern forms', founding his opinion, which I shared, on the fact that, whereas the intervening between Sibutu and Borneo appeared to be shallow, that between Sibutu and the Tawi-Tawi Islands was known to be of great depth, the charts showing 500 fathoms 'without bottom', so that this deep Sibutu Passage seemed to form the natural line of delimitation between the Bornean and the Philippine groups of islands and between their respective faunas. Captain Field, of H.M.S. Egeria, has been recently surveying this part of the coast of Borneo, and I suggested to him that it would be a point of some scientific interest to ascertain the real depth of the Sibutu Passage. This he very kindly did, with the result that the deepest sounding obtained was 267 fathoms, while one cast showed as little as 139 fathoms. Capt. Field informed me that he had sounded as nearly as possible on the spot where the chart records '500 fathoms—no bottom' without finding any such depth, and that he thought that the former record might have been due to errors arising from the less perfect sound¬ ing-apparatus in use in former days. But not only is the Sibutu Passage much shallower than Guillemard was led to suppose it to be, but Capt. Field's survey 011 the western side of the island shows that it is connected with the 100-fathom fringing bank of Borneo by a very narrow isthmus, 011 which the shallowest sounding seems to be one of 75 fathoms,—so that it can only lie said to be Original from and digitized by National University of Singapore Libraries No. IS ON THE GU1LLEMAKD ZOOGEOGRAPHICAL LINE—HACHISUKA 185

geographically a part of Borneo as defined by the 100-fathom line of soundings. I may mention that Sibutu is mainly composed of recent coral limestone, raised not many feet above the sea; but there is a hill of volcanic rock and crater-lake, which 1 did not myself see. The Tawi-Tawi Islands appear to be all either volcanic or recent limestone.''

There have been made no recent collections of birds from Sibutu and those of Oustalet, Guillemard, Blasius, Sharpe and Everett were secured a good many years ago. While it is desirable for a competent naturalist to explore this region once more, in view of the fact that the islands are small and would probably not offer very many new residential species, I am content with the material included in my book "The Birds of the Philippine Islands". The following list may not be exhaustive, but there is sufficient evidence whereupon to base a new line which I propose below. (a) Philippine species found in Sulu archipelago (including ) and Sibutu but not in Borneo.

1. Saematena melanospila bangueyensis. 2. Streptopelia dussumieri. 3. Prioniturus flavicans verticalis. 4. Tanygnathus lucionen&is mora. o. Pitta erytlirogastra. G. Pitta sordida. 7. Ixos everetti haynaldi. 8. Dicaeum sibutense. 9. Cinnyris jugularis jugularis. 10. Sarcops calvus. 11. Corvus coronoicles pliilippinus.

I have included (6) Pitta sordida in this list although this species is found both in Borneo and the Philippines, but this is the only species racially separated by the Sibutu channel. (b) In studying the above list the following three species are racially different as between Sulu (including Bongao) and Sibutu; while Vicaeum sibutense is confined to this region.

Sibutu Sulu (including Bongao) Pitta c. yairoclio. Pitta c. erytlirogastra.

Pitta s. muUeri. Pitta s. sordida.

Vicaeum s. sibutense. Dicaeum s. assimilis.

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(c) Philippine species found in the Sulu archipelago (includ¬ ing Bongao) and not westward of Sibutu.

1. Gallus gallus gallus (reappears 011 the Asiatic continent). 2. Hypotaenidia torquata. 3. Spilornis holospilus. 4. Ninox spilocapliala reyi. 5. Ducorpsius haematuropygius haematuropygius. 6. Tanygnatlius mullcri burbidgei. 7. LoriCulus pliilippensis bonapartei 8. Ceyx lepidus margaretliae. 9. Halcyon winchelli winclielli. 10. Dryobates ramsayi ramsayi. 11. Xeocephus rufus cinnamomeus. 12. Culicicapa helianthea panaycnsis. 13. Edolisoma morio everetti. 14. Minodonia striaticeps Iccttlewelli. 15. Copsyclius mindanensis. 16. Parus elegans. 17. Dicaeum hypoleucum. IS. Oriolus samarensis cinercogcnys.

(d) Species found in Sibutu but in neither Borneo nor the Philippines.

Otus manaclensis sibutensis

One has to remember Scops Owl is not easy to collect owing to its nocturnal habit and fast flight when flushed, and it is possible that its occurrence on other islands may have been overlooked by the naturalist spending only a limited time there. I therefore do not feel very confident that this record is important. A subspecies of Scops Owl, at present known from within the political limits of the Philippines, is 0. m. steerei from Tumindao Island and Sitanki Island. (e) Bornean species found in Sibutu and not in Sulu (in¬ cluding Bongao).

Orthotomus sericeus sericeus

The above species of Taylor Bird is a genuine Oriental species found in Tenasserim and Malay Peninsula through all the islands

* The Bongao form is probably a new race, Ibis 1894, p. 249. Original from and digitized by National University of Singapore Libraries .No. 1H ON THE CiUlLLEMAUD Z00UE0UKAPII1CAL LINE—11ACH1SUKA 187 to Borneo ancl , also Balabae, Calamianes and Sitanki. The categories above may be summarized into the following diagram. The total number of resident birds, those above men¬ tioned species found in the discussed areas are thirty-one.

Borneo i Sibuta Bongao Sulu i I 1 (a) 11 I 1 (c) IS I ! 1 (e) 1 | I 1 (d) 1 Guillemard Line

It will be noted from the above that the difference between bird fauna of Bongao and Sibutu are great and the sudden paucity in species on the latter island is prominent. The fact has already been clearly emphasized by Everett and oeeanographical research provides the reason. Sibutu species shown on table (a) contain abundant true Philippine genera such as Sarcops; and three genera of Cockatoo and Parrots of Australasian origin are never found anywhere else in the Oriental region, except in the Philippines and three small islands off Borneo and Java.

Moreover we are aware of the presence of an Indian species of a Parrot, Psittacula and Psittinus in the mainland of Borneo but it is not found in Sibutu. The only species of Bornean and Palawan birds found in Sibutu and not found in other parts of the Philippines is Ortliotomus cericeus but its allied species are commonly found throughout the archipelago. There is, therefore, a zoogeographical line of demarcation between Borneo and the Sulu archipelago, and this passes between the narrow strait separating the mainland of Borneo and the island of Sibutu.

It is my pleasure to name this—the Guillemard Line after Dr. F. II. II. Guillemard. This zoological boundary line continues in a northeasterly direction, leaving Cagayan Sulu on the Bornean side and all the Sulu Islands to the Philippine territory. This little island of Cagayan Sulu possessing few species of birds, however includes distinct Bornean species, such as Munia fuscans, Chocolate

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Weaver and Mixornis gularis cagayanensis the Tit Babbler. The latter was discovered and named afterwards by Guillemard. The occurrence of a small parakeet, Loriculus galgulus, is also suspected. Pycnonotus p. plumosus and Orthotomus sepium borneonensis un¬ changed from the Bornean individual, the species of which is not known from the Philippines proper. It is evident my theory does not agree with all my predeces¬ sors. It also contradicts a general rule of distribution, namely that the depth of the ocean is fundamentally more important than its width.

Sibutu, we understand, is a flat coral formation except that in the centre of the island there is a velocanic hill. This obviously indicated that the island is of recent formation geologically. The birds found there are sun-loving, lowland types although a few may be termed as true forest-loving birds. Their home is there¬ fore easily changed and they tend to migrate more readily than do the other rarer species confined to mountains or thick forests in . When I visited the Zoological Museum at Harvard University, I examined a small but interesting collection of bird skins obtained on Maratua Island. This island is believed to be of coral limestone covered by forest, situated 110 great distance from the shore of southeast Borneo but a great distance from the Sulu archipelago, yet it contains distinct Philippine elements amongst the sun-loving and lowland types of birds. How parrots and sunbirds can possibly migrate from the Philippines to Maratua Island without touching the mainland of Borneo remains a mystery still to be solved. In this connection we must remember the distribution of a Megapod, Megapoclius, which is common in all the islands in the Philippines and otherwise only on small islands off the coast of Borneo, yet a bird quite unknown on the mainland. Moreover the presence of Dicaeum sibwtense, the only Sulu archipelago species not found anywhere else, is found both 011 Sibutu and Bongao. It would be of great interest to know if such strange distribu¬ tions exist amongst other groups of the terrestrial animal kingdom Original from and digitized by National University of Singapore Libraries Xo. IS ON THE GTJILLEMARD ZOOOEOGRAPHICAL LINE—HAOHISTJKA 189

and whether they bear out the Guillemard Line as strongly as does ornithology. It will be noted from the above table that the avifauna of the Sulu archipelago is almost entirely composed of Mindanao elements and practically no Malayan elements have been derived from Borneo eastward. This strain of migration is extremely ancient. The area has been raised and depressed, not once but several times, so that it is reasonable to suppose that its fauna and flora have at times been partly or entirely destroyed by natural causes. It should be noted that the Sulu Hornbill, Limnophalus, underwent generic isolation and Otus rufescens is subspecifically different between Sulu and Borneo. The Brown Ground Thrush, Zoothera, of Java, Sumbawa, Lombock and Timor reappears on Mindanao mountains. Moreover an aberrant white-eye, Oreosterops, of Mindanao mountains reappears as different species in Java, Sumbawa, Flores and Ceram. It is worthy of note that this thrush and white-eye are not known from both Borneo and Celebes. As Burbidge remarked that Sulu shows close floral affinity to Celebes, a few words should be devoted to that subject. For the best example of Sulu-Celebes affinity I do not hesitate to indicate Ptilinopus temmincki. This distinct species of small Fruit pigeon is found nowhere but in Sulu and Celebes while the allied geo¬ graphical species P. superbus is common in Papuasia and Moluccas. The range of the Imperial Pigeon, Ducula cineracea, is somewhat the same as Ptilinopus. Coracina straiata guillemardi of Sulu is extremely similar to C. s. personata of Roma and Timor, but perhaps more like C. s. pollens of Key Island although the latter is large in size.

We are aware that Otus man a dens is of Celebes and Moluccas

is represented in the Philippines, as far as our present knowledge goes, only in Sibutu and Tumindao. The avifauna! distribution of the Sulu archipelago including the island of Sibutu is therefore to be regarded as an extension of Mindanao avifauna, but owing to its small broken up surface, it proves to be poor in indigenous species. Bornean species are feebly represented while it is worthy of note that a few but distinctly Celebean species, unknown in Mindanao, are found in

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this group. Generally speaking, avifauna in the Philippine archipelago is richer than that of Borneo and its surrounding islands. It is true that Indian members are common in Borneo, and we may take as an example a characteristic Oriental family Timaliidae, whose genera, Garrulax, Malacocincla, Malacopteron and Alcippe are com¬ monly found in the tropical part of the Asiatic continent through¬ out the Malay archipelago to Borneo, however none to them are found in the Philippines. Another example may be drawn from large-sized members of the game birds. Many genera of pheasants and partridges are known in Borneo while none of their species are found in the Philippine islands. . Members of Pycnonoticlac are also outstanding in this respect. However, it is interesting to know that many common Philippine genera are also common 011 the large Sunda islands excepting only Borneo, the reasons for which are still to be determined. Those genera are Gallus, Turnix, Pelecanus, Tyio, Xantholaema, Megalurus and Cisticola. Celebes has all those representatives except Pelecanus and Xantholaema while Gallus is considered to be of introduced origin. I have included below in the form of a table a few examples of families found both in Borneo and the Philippines, clear evidence that the Philippine archipelago is much richer in its possession of a greater number of species and subspecies in comparison to Borneo.

BORNEO, NATUNA PHILIPPINE Families & other neighbouring ISLANDS islands

Species aiul Species and Subspecies Subspecies Columbidae 24 31 Strigidae 13 23 Alcedinidae 13 2d Muscicapidae 43 57 Dicaeidae 14 35

The total number of birds known from Borneo and its sur¬ rounding islands including Natuna Island is 675 species and sub¬ species, while the total number known from the Philippine Islands is 818. It is interesting to know furthermore than not more than Original from and digitized by National University of Singapore Libraries No. IS 0N THB GUILLEMARD ZOOUEOUKAPIIICAL LINE—I-IACI-IISUKA 191

308 species ancl subspecies are known to exist from Celebes, up till this day. Dr. B. D. Merrill, an authority 011 Philippine flora, published a lengthy paper in 1!)23 in the Philippine Journal of Science, discussing the distribution of Dipterocarpateae, and highly recom¬ mended to students interested in the problem of life changes in the . Like Guillemard, Everett and others, Merrill accepted Sibutu Passage as his line of demarcation, chiefly on the basis of the hydro- graphic data while he did not have any comprehensive botanical collection from small islands in the vicinity. Further his line ex¬

tends in a northeasterly direction passing between Palawan and and Formosa and , regarding it as an extension of the Wallace Line, instead of its passing directly eastward separat¬ ing Celebes in the south from Borneo and the Philippines. Ornithological(v speaking, Dr. Merrill's theory will constitute the main Philippine boundary and his proposed line may well be accepted with slight modifications; but if we are considering the major zoological divisions of the world, 1 retain conservatively Wallace's original line proposed by Huxley, maintaining that the Philippines belong to the Oriental region rather than to the Australasian. The Philippine fauna is a strange admixture of elements from both regions and it is a natural melting pot for all the animals and plants poured into it from the Indian and Australian continents over the Malay-Bornean and Papuan-Celebean stepping stones, and both strains are amazingly well blended. Of all the Philippine families of birds, the following two are not found in the Australasian region :

1. Trogonulac 1 species, general distribution. 2. Eurylaemidae 2 species, general distribution

The following two are not found in the Oriental region (excluding Palawan subregions—-Bali and Solombo Besar in Java Sea) :

3. Kakatoeiilac 1 species, general distribution. 4. Loriidae 1 species, limited distribution.

3 and 4 are Cockatoo and Lory and much the same group of Original from and digitized by National University of Singapore Libraries 102 bulletin oe the biogeog11aphical society oe japan vul- (i

families while the latter is restricted to the two mountains in

Mindanao. 1 and 2 are both generally distributed throughout the Philippine archipelago while 2 is an endemic genus. Sarcophanops includes two distinct species. It proves clearly that the Oriental element is very slightly predominant and that the Australasian

strain is a little inferior.

If further one studies genera and species of residential land birds, the above fact becomes more emphasized showing that the Philippine avifauna and its affinity is within the limit of the vast Oriental region. Furthermore this fact amazes us all the more when we realize such an almost equal amount of incoming strains and blending which has taken place in the past has produced a rich and distinct avifauna within a comparatively small yet much broken up geographical area, a most unique feature when com¬ pared to any other part of the world equal to it in size.

The Biogeographical Society oe Japan

c/o Hachisuka, Mitatsunamachi, Shibaku, Tokyo, Japan September 10 1936 30 sen

The Sanshusha Press Tokyo Original from and digitized by National University of Singapore Libraries