Notes on the foraging and feeding behaviours of the Asian Openbill Stork (Anastomus oscitans)

The foraging and feeding behaviours of the Asian Openbill Stork (Anastomus oscitans) were observed in several paddy fields in Thailand, on food items not previously reported. Foraging and feeding techniques of the storks were similar to those described in the literature, except at one site where a peculiar new foraging behaviour was observed. Here, the storks fed on exotic Golden Apple Snails (Pomacea canaliculata) by using their bills to puncture the shells for extracting the soft snail bodies. The shells of large snails discarded by storks tended to be more damaged than those of small snails, due to the difficulty of extraction. Analyses of stork’s droppings and their regurgitated food showed that the bulk was of plant materials and shelled snails (mainly P. canaliculata and Filopaludina spp.). Adult storks tended to consume the whole soft bodies of the snails, including viscera, and sometimes the entire snails, including with their hard shells and opercula still attached. Although the storks could feed potentially on the entire snail body, the birds were seen to discard the male’s testes and female’s albumen glands of P. canaliculata at these feeding grounds, also evident in their regurgitates. Crushing of snail shells was not evident, but sometimes, pounding the shell and/or swallowing the entire shell and its operculum were supported by observations.