This is one of two species of stork in the genus Anastomus which have a peculiar gap between the mandibles. The other is the African Openbill (Anastomus lamelligerus).
The oddly shaped bill facilitates foraging on Apple Snails of the genus Pila. The snail is held in the upper mandible and the lower mandible punctures the hard operculum while a salivary secretion from the stork relaxes the snail's tough muscle. Typically the snail is removed from its shell without damaging the shell at all. These snails are immune to almost all other forms of predation, so these storks are an important population check on the snails.
Although this species is declining in part of its range, it remains common and conspicuous around the Bangkok Airport where it can pose a danger to aircraft.
This grayish individual is an immature and is perched atop a dead palm stalk in a vacant lot near our hotel. The adult is whiter.
Digiscoped with Panasonic DMC-LX5 | Nikon FieldScope III | 30XWA | hand-held (no adapter).