The global proliferation of invasive freshwater mollusks poses a significant threat to agricultural productivity and ecosystem health, yet the specific behavioural adaptations that allow native predators to exploit these novel resources remain a critical research gap worldwide. In Peninsular Malaysia, the Asian Openbill (Anastomus oscitans), a specialist molluscivore is increasingly observed in rice fields preying on invasive apple snails (Pomacea spp.), which have become major pests since their introduction from South America. This study investigates the foraging behaviour and predatory efficiency of Asian Openbill across 70 locations to evaluate their potential as sustainable biological control agents and to address the lack of scientific research regarding their ecological impact in the region. Foraging activity was recorded in relation to habitat conditions, time of day, and prey type. The storks were observed primarily targeting juvenile and mature male snails while avoiding egg-bearing females, likely due to the known toxicity of their eggs. Unlike previous reports, the Openbills did not swallow small snails whole; instead, they removed the operculum and extracted the soft tissue, discarding the shells, highlighting a specialized feeding technique. Foraging intensity was highest in fields with shallow standing water, where prey accessibility was enhanced. Storks were significantly less active in dry fields, where they tended to perch or rest. Peak foraging occurred during mid-morning (0900–1000 hours) and mid-afternoon (1400–1500 hours). Shell remains were collected from a 200-meter transect in Sungai Manik, Perak, totaling 547, with a mean shell length of 31.6 mm, indicating frequent predation of medium-sized snails. In contrast, fields in Sungai Besar, Selangor recorded only seven small live snails (average 25.1 mm) and no shell remains, suggesting either low snail presence or limited predation. Sites without Openbill presence had significantly higher live snail counts (n = 88), while fields with active Openbill foraging showed fewer live snails, damaged shells, and missing operculums supporting the bird's role in reducing snail populations. These findings provide preliminary evidence that Asian Openbills exert a measurable impact on Pomacea density and could be integrated into rice pest management frameworks. This research demonstrates the ecological relevance of Asian Openbills in rice field ecosystems and supports their consideration as a sustainable, non-chemical alternative to conventional molluscicides. Further studies, including quantitative assessments of predation efficiency and long-term monitoring, are recommended to fully establish their utility in integrated pest management programs.
Anastomus oscitans, Foraging ecology, Iinvasive species control, Molluscivore, Rice agroecosystem
