Asian Openbill - Food and Foraging

Food and Foraging

The Asian Openbill like many other storks forages at wetlands, reaching them by flying with wing flapping interspersed with gliding. During the warmer part of the day, they also soar on thermals and have a habit of descending rapidly into their feeding areas. Groups may forage together in close proximity in shallow water or marshy ground on which they may walk with a slow and steady gait. The Asian Openbill feeds mainly on large molluscs, especially Pila spp., and they separate the shell from the body of the snail using the tip of the beak. The tip of the lower mandible of the beak is often twisted to the right. This tip is inserted into the opening of the snail and the body is extracted with the bill still under water. Jerdon noted that they were able to capture snails even when blindfolded. The exact action being difficult to see, led to considerable speculation on the method used. Sir Julian Huxley examined the evidence from specimens and literature and came to the conclusion that the bill gap was used like a nutcracker. He held the rough edges of the bill as being the result of wear and tear from such actions. Subsequent studies have dismissed this idea and the rough edge of the bill has been suggested as being an adaptation to help handle hard and slippery shells. They forage for prey by holding their bill tips slightly apart and make rapid vertical jabs in shallow water often with the head and neck partially submerged. The gap in the bill is not used for handling snail shells and forms only with age. Young birds that lack a gap are still able to forage on snails. It has been suggested that the gap allows the tips to strike at a greater angle to increases the force that the tips can apply on snail shells. Smaller snails are often swallowed whole or crushed. They also feed on water snakes, frogs and large insects.