Written by: Sandy Leo Bawean Island (Fig. 1) is an island in the middle of the Java Sea, very isolated from Java and Kalimantan mainland. This island distance is around 120 km from Java Island and 300 km from Kalimantan Island. Based on biogeographic studies, Bawean Island disconnected from Java about 10000 years ago. This condition makes Bawean Island having a very high endemism in both flora and fauna.
Fig 1. Bawean Island
The 10th of August 2015 was a very lucky day for us (BEKI Team). After doing a pig survey, we were surprised by big eyes among the tree branch. Yes!!! That’s the owl we were looking for, the spotted wood owl. Pak Rahim, our forest ranger, said the local people called it kukuk beluk. Spotted wood owl (Strix seloputo) maybe looks similar with the Barn owl (Tyto alba) from its round face and body, but it shows some significant differences. The most distinct difference is from spotted pattern on the body, while the barn owl has no spots.
Fig. 2 Spotted wood owl Strix seloputo baweana (left) and barn owl Tyto alba (right) (photos Putri Diana and Sandy Leo)
According to Avibase (Lepage 2015), Strix seloputo has 3 subspecies, named S. seloputo seloputo (South Myanmar, Malay Peninsula, Sumatera and Java), S. seloputo baweana (Bawean Island) and S. seloputo wiepkeni (South Philippines). Strix seloputo baweana has different morphological variation than the original subspecies. Hoogerwerf (1967) also described and measured S. seloputo baweana has a smaller body size than the other species. That indicates that isolated areas make the birds to evolve and adapt with small area and not much preys variation. Nijman (2004) also mentioned that the spotted owl on Bawean probably has a large distribution over the island, but very little is known about their detailed abundance and distribution. There is a need for more research including surveys and monitoring to get to know more about the abundance and distribution of this beautiful endemic bird. Knowledge about the abundance and distribution is necessary to make effective conservation action plan in order to protect this endemic bird from potential threats to its longterm survival.
If you want to read further: Hoogerwerf, A. 1967. Notes on the island of Bawean (Java Sea) with special reference to the birds. Natural History Bulletin of the Siam Society22:15–104 pp. Lepage, D. 2015. Avibase – the world bird database. http://avibase.bsc-eoc.org/species.jsp?avibaseid=95C18369B3D381CF. [accessed on Sept, 4th 2015] Mayr, E. 2001. What Evolution Is. Basic Books, New York: 318 pp. Nijman, V. 2004. Survey of birds of prey and owls (Falconiformes and Strigiformes) on Bawean, Java Sea, with records of three species new to the island.TheRaffles Bulletin of Zoology52(2): 647–651.