Waterbird community in Pulau Rambut Wildlife Sanctuary, Jakarta Bay: Review on species composition and population size after thirty years

Abstract

In the Jakarta Bay area, Pulau Rambut, a 25-ha island, has been known as an important breeding/nesting site for 15 waterbird species. Land-use change and habitat deterioration potentially have some impact on the waterbird population. The objective of this research was to compare species composition and population size of waterbirds nesting in Pulau Rambut after 30 years (1990-2020), and provide an analysis on the possible causes of the change. Secondary data on population size and species composition were used for analysis. Habitat changes in the foraging habitat were observed intermittently. Black-headed ibis and Little-pied cormorant were extirpated from the island, thus the species number was decreased to 13. Population size of all waterbirds was greatly decreased (from 10,180 to 4,950 individuals). However, the population of the endangered Milky stork has increased, from 24 (0.2%) to 78 (1.6%) individuals, possibly due to additional birds migrating from the eastern coast of Sumatra. There was a significant change in the species composition (paired t-test; t=0.488, P<0.01), with Cormorants still dominated the community. Possible causes of the population decrease were the shrinking wetlands in Java as waterbirds’ foraging habitat, and deterioration of mangroves as nest trees in Pulau Rambut due oil pollution.