|Abstract||The Island of Billiton is situated between Sumatra, Borneo and Java. From a geological point of view, it may be considered to be a continuation of the chain, formed by the Malay Peninsula, the Mountains of the Riouwand Linga Archipelago and of the Island of Banka, from which latter it is separated by Strait Gaspar, while the tolerably broad Karimata Passage separates it from Borneo. Although Billiton lies in the centre of a zoologically tolerably well-explored region, the fauna of this island was still unknown. That was the reason for my visit to the island in the month of June 1888, during which time I not only travelled through the greater part of it, but also chanced to cross to the neighbouring Island of Mendanao, where I spent three days in the vicinity of the light-house, situated on the mountain-ridge. This tolerably large island belongs to the same geological formation as Billiton, and is separated from this latter island by a narrow passage.|
The ornithological collection, brought together during my stay on Billiton and Mendanao, contains not a single species of which the habitat is restricted to these islands. Of the 93 species, contained in the list, there are 32 which are not found in Java, 10 which are not found in Borneo, 8 are not known from Malacca, and only 5 not from Sumatra. The avifauna of Billiton, therefore, seems to agree more with that of Sumatra than with that of Malacca, less with that of Borneo, and the least with that of Java. To my and my huntsmen’s astonishment we found no crows on the islands, nor any species of Ploceus, nor Sturnopastor jalla and melanopterus , nor Acridotheres griseus, all of them species which are tolerably common in Java.