NOTES ON ZOOGEOGRAPHY

The avifauna of Borneo is of Indo-Malayan affinities. The number of birds endemic to Borneo is relatively small; most species are shared with the Asian mainland. Only 29 birds are known to be endemic to the island and 17 of these are montane. The large proportion of montane endemics is not surprising, because Borneo has been connected with the Asian continent in recent geological time; lowland isolation, and differentiation, has been less extensive than the montane. The Sunda Shelf, on which Borneo is situated, lies in a shallow sea generally less than 300 feet deep. Beaufort has shown that the Malay Peninsula, Sumatra, and Java were connected until early historic times (Darlington, 1957:488).

The endemic species in Borneo are members of four, possibly five, genera that are also endemic. Four of these five genera are montane in distribution. The only endemic for which the geographic history cannot be adequately explained is the monotypic Pityriasis gymnocephala. Its affinities seem to be with the Cracticidae of New Guinea and Australia. The species has been found throughout Borneo. Since Pityriasis is endemic to Borneo, it probably was detached from the parent stock at an early period. The Australasian affinities of Pityriasis emphasize its zoogeographical peculiarities. A more detailed discussion of this species appears in the annotated list below.

COLLECTING LOCALITIES AND COLLECTORS

Fig. 1. Localities from which collectors from the Department of Agriculture or I saved specimens in North Borneo.

1. Cocoa Research Station, Quoin Hill, elevation 750 feet, Tawau. Max C. Thompson (MCT) and Antonio D. Garcia (ADG).
2. Tawau. Max C. Thompson.
3. Twelve miles north of Kalabakan, elevation 600 feet. Max C. Thompson.
4. Kalabakan, elevation 50 feet. Max C. Thompson.
5. Tiger Estate, 20 miles northwest of Tawau. Max C. Thompson, Antonio D. Garcia.
6. Ulu Balung Cocoa Estate, Mile 27, Quoin Hill, elevation 750 feet, Tawau. Antonio D. Garcia.
7. Karindingen Island. Max C. Thompson.
8. Siamil Island. Max C. Thompson.
9. Lahad Datu. Antonio D. Garcia.
10. Kuala Sumawang, 25 miles west of Sandakan. Antonio D. Garcia.
11. Agricultural Station, Mile 17, Sandakan (Gum-Gum). Antonio D. Garcia.
12. One-fourth mile east Gum-Gum, Sandakan. Antonio D. Garcia.
13. Lamag, Kinabatangan River. Antonio D. Garcia.
14. Pintasan Agriculture Station, Kinabatangan River. Antonio D. Garcia.
15. Kampong Kuamut, Kinabatangan River. Antonio D. Garcia.
16. Kampong Maluwa, Kinabatangan River. Antonio D. Garcia.
17. Ka-Karis, Kinabatangan River, elevation 200 feet. Antonio D. Garcia.
18. Tongod, Kinabatangan River, elevation 300 feet. Antonio D. Garcia.
19. Tuaran. Max C. Thompson, Antonio D. Garcia, S. F. W. Chong (SFWC).
20. Telipok. Antonio D. Garcia, G. R. Conway.
21. Mt. Rumas, 5 miles northwest of Tuaran, elevation 75 feet, Antonio D. Garcia.
22. Five and one-half miles southwest of Tenom, elevation 4,000 feet. Max C. Thompson.
23. Tenom, elevation 600 feet. Max C. Thompson.
24. Kampong Banjar, Mile 29, Keningau. Antonio D. Garcia.
25. Oil Palm Research Station, Mile 32, elevation 40 feet, Sandakan. Antonio D. Garcia.

ECOLOGY OF THE COLLECTING LOCALITIES

Quoin Hill.—At this locality I recognized five habitat types as follows:

Primary forest.—We were fortunate to be able to work at Quoin Hill because it had been opened to cultivation (of Cocoa, Theobroma cacao) for only a few years. Thus the primary forest here started at the edge of the Cocoa Research Station. This was in marked contrast to areas on the west coast, where one would need to travel many miles inland to find virgin forest. The forest at Quoin Hill was typical tropical rain-forest, composed mostly of dipterocarps (Dipterocarpaceae). These comprise an essentially Indo-Malayan family, members of which are so conspicuous that we commonly referred to it as Evergreen Dipterocarp Forest. The lowland forests of Borneo are composed of approximately 3,000 species of trees (Browne, 1955). At Quoin Hill, as in most of the tropical rain-forest of Borneo, the forest canopy is stratified in three layers, a distinct and easily recognizable top story and less easily separable middle and lower stories. The top canopy is composed of foliage of giant trees that may tower to heights of 200 feet and have trunks three to seven feet in diameter. The trunk is usually unbranched for 50 to 100 feet and the whole tree is supported by buttresses jutting out from the main trunk. Some of the most important plants in the tropical rain-forest are the strangler figs (Ficus sp.). These plants, when in fruit, draw birds in large flocks to feed upon them. Such figs were common about the edges of the research station and some birds taken from these trees were never taken elsewhere. The birds seemed to wait for a certain degree of ripeness of fruits; on one day the figs were unmolested and the next day the trees would be swarming with birds. Strangler fig trees reach tremendous size and help form the upper forest canopy.

The middle and lower forest canopies are not easily separable and I shall speak of them together. The trees forming these varied from 10 to 60 feet in height. The ground surface beneath the trees was usually bare except for leaf litter and dead branches. Sunlight penetrates only where the big trees have been removed or where the larger trees are otherwise widely spaced. At Quoin Hill the large trees of species affording lumber of commercial quality had been taken out, modifying somewhat the character of the forest. Such forest actually contained many of the animals characteristic of primary forest, and I refer to it as badly disturbed primary forest.

Secondary forest.—In some of the areas adjoining the research station, roads had been bulldozed for future expansion and trees had been cut. These areas were starting to grow dense stands of grass and shrubs and will be jungle in a few years unless cut back. Most of the trees in this area are saplings with some trees as large as a foot in diameter.

Fluviatile waters.—There are numerous small streams in the Quoin Hill area, the largest being the Balung River and Apas River. Little work was done along these streams and only the thrushes of the genus Enicurus and some kingfishers seemed to be confined to them.

Cocoa plantations.—Artificial plantings of cocoa, Theobroma cacao, formed a major habitat type at Quoin Hill, and provided a major source of food for birds. Cocoa planters have found it necessary to provide shade with trees of some other species. In some instances trees from the original primary forest were left standing to provide this shade, but more often exotic trees were planted. Most of the shade trees were of no use to birds save for providing resting places. Trema orientalis was the most important in providing food for birds. Its fruit was used more by the frugivorous species of birds than that of any other tree in the cocoa plantings. Tree Cassava, an exotic, was constantly attended by the nectariniids, or honey creepers.

Although the cocoa plantings did not provide much plant material for bird food, they did apparently nourish a horde of insects, which the