Abstract
I often find myself traveling thither and yon on one sort of mission or another. The advantage is that I can usually manage to visit bird-related people and places while still attending to the task at hand.
Just a few weeks ago, having completed inescapable duty in the Philippines, I thought about the zoogeographical region of this issue - the southeast Asian peninsular area from northern Thailand, Laos, and Vietnam south through Malaysia to Singapore then the islands of the Malay Archipelago as far east as Bali.
Why stop at Bali, you say, right in the middle of Indonesia? Actually, because of the Wallace's Line. What, pray tell, is the Wallace's Line and why do we stop there? Good questions.
In 1856 an Englishman, Alfred Russel Wallace, after three years of Malay travels, was working his way from the Malay Peninsula down through the islands of the Malay Archipelago. Because of the Dutch and English settlements in the area, the birds of the
region were quite well known. When Wallace reached Bali, he noted many of the same birds that were also found on Java lying just to the west across a narrow strait.
However, when Wallace went eastward to Lomboc he made an unexpected discovery. He later wrote:
On crossing over to Lomboc, separated from Bali by a strait less than twenty miles wide, I naturally expected to meet untb some
of these birds again; but during a stay there of three months I never saw one of them, but found a totally different set of species, most of which were utterly unknown not only in [aia, but also in Borneo, Sumatra, and Malacca.
Most noticeable, perhaps of the "new set of species" on Lomboc were the white cockatoos more commonly associated with Australia. Some sort of "line" had been crossed.
This line became known as Wallace's Line in honor of the first fel-
low to recognize and publicize it. Observe the map above and see the clearly marked Wallace's Line.
Later scientists determined that the secret of the Wallace's Line is really deep water. The islands to the west of the line are on the continental shelf with Bali being right on the edge of the shelf. Lomboc, to the east, is not on the shelf at all but rises from the deep sea. The Wallace's Line traces the path of the deep water. It marks the boundary between the Asiatic and Australian birds (as well as other flora and fauna).
The islands on the shelf were at one time all connected by land to the Malay Peninsula, thus Bali shares many of the animals and plants found on Java, Sumatra, and the Malay Peninsula.
Note that the Philippines are on the Australian side of the line - with the exception of the pristine island of Palawan which is influenced by both the Australian and Asian sectors. For that reason, I felt it appropriate to include an article on the Red-vented Cockatoo - the only white cockatoo
found in the zoogeographical region of this issue.
Although this minor treatise of the Wallace's Line is overly simplified, you can easily see why the zoogeographical focus of this issue stops at Bali.