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
birds fed upon. A Drongo-cuckoo, _Surniculus lugubris_, had 50
caterpillars in its stomach. Healthy cocoa trees were sparsely inhabited
by birds but areas that were obviously infested with insects literally
swarmed with birds. Dead shade trees in the cocoa plantings also
provided food for woodpeckers, with four species being found utilizing
these dead trees.
_Abaca._--The last of the habitat types that I recognized at Quoin Hill
was a small grove of Abaca, _Musa textilis_, and wild bananas, _Musa_
sp. This habitat type was frequented by spiderhunters (_Arachnothera_
sp.) of the family Nectariniidae.
KALABAKAN.--We worked at three localities in this area: 12 miles north
of Kalabakan, Brantian Estate, and Kalabakan.
_Primary forest._--We were fortunate in being able to work on the very
edge of the primary forest 12 miles north of Kalabakan. The composition
of the primary forest was much like that at Quoin Hill and will not be
discussed further. About a month after we arrived at our forest camp,
logging crews moved in and cut the commercial timber near our area. The
only immediately noticeable difference in the makeup of the avifauna
after destruction of the forest canopy was the appearance of the drongo
_Dicrurus aeneus_. This drongo was seen in areas where the trees had
been cut, sitting on limbs and darting out after insects.
_Secondary forest._--The area around Kalabakan proper was in secondary
forest, which was almost impossible to penetrate. At Kalabakan,
_Cymbirhynchus macrorhynchus_, _Cecropsia striolata_, and _Macronous
ptilosus_ were taken and I did not see them elsewhere. Kalabakan is
situated on the Kalabakan River at the upper tidal limit. The
Nipa-Mangrove association, not investigated, lies immediately below
Kalabakan.
The Brantian Estate area was mostly in secondary forest and was situated
on the Brantian River. There were some fairly large areas of grass with
water buffalo wallows in them. These grassy areas were favorite haunts
of the Painted Quail, _Coturnix chinensis_.
TENOM.--The first locality that we investigated was 5.5 miles southwest
of Tenom, approximately 4,000 feet elevation, in moss forest. A few days
were spent collecting in the area of Tenom itself.
_Moss forest._--The lower altitudinal limit of the moss forest was about
3,600 feet. The trees on top of the mountain were mostly oaks
(_Quercus_) and were festooned with ferns, orchids, and other epiphytes.
The area had been used as a triangulation station by a survey team and a
small area on top of the mountain had been cleared earlier. At the time
of our visit this small area had grown to secondary vegetation, mostly
_Pandanus_. The oaks in the primary forest surrounding this disturbed
area were generally about 30 to 50 feet high and there was little
undergrowth in virgin stands. This area was usually swathed in fog from
three o'clock in the afternoon until eleven o'clock the next morning.
One morning of our fourteen there was clear.
_Paddy._--The area visited at Tenom itself consisted mostly of old paddy
grown to grass and scrub. Forest did occur but was of secondary nature
in the immediate vicinity of Tenom.
SIAMIL ISLAND.--This island is about one mile in circumference and the
highest point is about 300 feet above sea level. The island has high
bluffs on three sides but slopes gently to the sea on the other. There
were patches of forest left on the island, one on the north side and one
on the south. The sheer bluffs on the east side of the island were
covered with _Pandanus_ sp. The undergrowth of the north forest had been
cut, leaving extensive bare areas. The principal undergrowth was rattan.
The natives are clearing and planting more of the island to coconuts and
hope eventually to clear it completely.
KARINDINGEN ISLAND.--This island, about half a mile in circumference and
between 10 and 20 feet above sea level at its highest point, was
surrounded by extensive coral reefs and sand; the principal vegetation
was mangroves.