Distribution pattern and abundance dynamics of Asian Openbill (Anastomus oscitans) in rice field throughout Peninsular Malaysia

The Asian Openbill (Anastomus oscitans) plays a crucial role in rice field ecosystems by preying on invasive apple snails (Pomacea spp.), potentially reducing the reliance on chemical molluscicides. This study investigated the distribution and abundance dynamics of the stork across major rice granaries in Peninsular Malaysia. Surveys were conducted at 111 sampling points within 30 localities across 11 states during five consecutive rice seasons (2022–2024), with bird counts obtained through binoculars and digital photography. Results indicate that storks are highly concentrated on the northern and central west coasts, where rice fields provide abundant foraging opportunities. In the northern regions (Perlis, Kedah, and Seberang Perai, Penang), the stork populations are likely migratory, whereas the central regions (Sungai Besar, Selangor; FELCRA Seberang Perak, Ulu Dedap, and Sungai Manik, Perak) host resident populations, with nesting activity recorded at Pulau Bangau, Teluk Intan. In contrast, the species was recorded in low numbers in Melaka and was entirely absent from Negeri Sembilan and Johor, despite documented sightings between 2019 and 2020. On the east coast (Kelantan, Terengganu, and Pahang), storks were present in lower densities, mainly as migratory individuals. Seasonal patterns indicate peak abundance during the main rice season (August–March), aligning with their migratory cycle. The storks’ distribution closely reflects the availability of apple snails, suggesting a spatial relationship driven by the abundance of prey. This highlights the ecological role of rice fields in sustaining both migratory and resident populations. The findings provide valuable insights for conservation planning and the integration of sustainable rice farming practices to support biodiversity while managing pest populations.