The Asian Openbill: The Stork with a Gap in Its Beak, Photographed near Gohpur, Assam

The photograph was taken near Gohpur, on the north bank of the Brahmaputra in Assam. A stork has just landed on a high branch, with its wings still raised and spread out. The flight feathers are dark grey to black, the inner wing is white, and the legs are pinkish. The most important detail is in the bill. Even when the bird closes it, a narrow gap of light shows between the upper and lower halves.

That gap gives the bird its name. This is the Asian openbill (Anastomus oscitans), one of the most common storks in the paddy fields and wetlands of Assam. Plenty of people in rural Assam see it often, but few know that its odd bill is one of the most specialised feeding tools in the stork family.

What the photograph shows

The bird has just landed, or is about to take off. Its wings are fully spread, so you can see a clear contrast in the plumage. The long primary and secondary feathers along the edge of the wing are dark with a slight sheen, and the coverts closer to the body are white. Its tail is black, and the body and neck are a soft smoky grey.

That grey shade matters. Asian openbills change colour through the year. In the breeding season the body becomes much whiter and the legs turn redder. Outside it, the body and back are greyish. Juveniles are browner. The bird here has a grey body, a clear gap in the bill, and pinkish legs, which suggests an adult that is not in full breeding plumage. Without the date, that can’t be confirmed.

The bird is perched in a tall tree with long leaves growing in whorls, the pattern typical of Alstonia scholaris (the devil’s tree, known locally as chatiana). That is not surprising. Openbills roost and nest high in large trees close to wet fields and wetlands. Gohpur and the surrounding area have plenty of both.

Identifying the Asian openbill

Feature	Description
Scientific name	Anastomus oscitans
Family	Ciconiidae (storks)
Size	About 81 cm long and 68 cm tall; small for a stork
Plumage	White to greyish-white body; black wing feathers and tail
Bill	Dull greyish-horn colour, with a gap between the closed mandibles in adults
Legs	Pinkish-grey, turning redder before breeding
Range	South and Southeast Asia, from India and Sri Lanka to Thailand, Cambodia and Vietnam
Global status	Least Concern (IUCN Red List)

The name says something about the bird too. Anastomus comes from Greek and is usually translated as “with the mouth open”. Oscitans is Latin for “yawning”. So the scientific name means roughly “the yawning stork with the open mouth”.

Hidden truths about the openbill

1. The gap is not there from the start

Openbill chicks are not born with the gap. Young birds have bills that close normally. The gap develops gradually as the bird grows, and young birds without one can still catch and eat snails.

2. The bill is not a nutcracker

For a long time people assumed the gap worked like a nutcracker, holding the snail between the two jaws and cracking it. Biologists have since rejected that idea. The openbill usually takes the snail’s body out without breaking the shell at all.

Observers have described the method in detail. The bird holds the snail on the ground or underwater, slides the tip of its lower bill into the shell opening (often turned to one side), and pulls out the soft body. The empty shell is left behind, often undamaged. In fields where openbills have been feeding, you can sometimes find heaps of intact empty snail shells.

Two explanations have been proposed for why the gap helps. One is that it lets the tips of the bill meet a shell at a sharper angle, which gives better control. The other is based on the edges of the bill, which have fine, brush-like ridges. These may help the bird grip a smooth, wet, slippery shell. Neither explanation is fully settled.

3. It may feed partly by touch

Thomas Jerdon, a 19th-century naturalist in India, recorded that openbills could still catch snails when blindfolded. In muddy water a bird can’t see its prey anyway. The openbill sweeps and jabs its bill through shallow water with the tips slightly apart, and appears to rely heavily on touch.

4. Snails are its main food, but not the only one

The Asian openbill’s diet is dominated by large freshwater snails, especially apple snails of the genus Pila. These live in paddy fields, ponds and the slow edges of wetlands. It also eats frogs, crabs, water snakes and large insects. Smaller snails are sometimes swallowed whole.

In Thailand, researchers have studied the openbill as a predator of the golden apple snail (Pomacea canaliculata), an invasive species that damages rice crops. That makes the bird interesting to farmers as a possible natural form of pest control. In India, though, the openbill is valued mainly for its role in wetland food chains, not as pest control.

5. It is one of India’s success stories

Many Indian water birds are declining. The Asian openbill is not one of them. The State of India’s Birds 2025 report classes it as a low conservation priority, with a very large range and a strong increase over the long term. Rice paddies, irrigation channels and village ponds all suit a bird that eats snails, and the openbill uses that farmland well. Its current year-to-year trend is listed as inconclusive. Long-term success does not mean it can be taken for granted.

6. It travels further than people expect

The openbill is usually described as a resident species, but it moves long distances in response to rain and food. Birds ringed at Bharatpur in Rajasthan have been recovered about 800 km to the east. A bird ringed in Thailand was found about 1,500 km away in Bangladesh. Like other storks, it rides thermals (rising columns of warm air) and can soar for long periods with very little flapping. Flocks circling high over the fields of Assam in the late morning are usually doing exactly that.

7. It was once hunted for food

In colonial India, hunters shot openbills for meat. Some called it the “beef-steak bird”. Hunting of openbills still happens in parts of the Northeast. Conservationists have publicly asked villagers not to kill or eat the birds, for example after a breeding colony was recorded in Tinsukia district in 2026. All wild birds in India are protected under the Wild Life (Protection) Act, 1972. Killing or capturing them is an offence.

Openbills in Assam

The Asian openbill breeds in colonies. Pairs build stick platforms close together in large trees, sometimes sharing the tree with egrets and cormorants. In northern India and Nepal, breeding mainly takes place during the monsoon, from about July to September. Assam’s colonies are active around the same time. The clutch is usually two to four eggs, and both parents share about 25 days of incubation.

Some colonies in Assam are well known. At Na-mati near Nazira, in Sivasagar district, large numbers of openbills come back to tall trees beside the Dikhow river each monsoon. Local people there have protected the colony, for example by avoiding firecrackers during Diwali. In 2026, about 100 openbills were recorded breeding in a single tree in Sumoni Bandarkhati village in Tinsukia district.

Colonies close to people need care. A study of colonies in Nepal found that breeding success was lower where nests were closer to human settlements. Cutting tall nesting trees, cutting branches in the breeding season, and noise directly below the nests all reduce how many chicks survive.

How to watch and photograph openbills responsibly

• Keep your distance from nests. In the breeding season, disturbance can make parents leave eggs or chicks exposed. A telephoto lens lets you photograph from far enough away.
• Look for them in the fields. Openbills are easiest to watch feeding in wet paddy fields or at the edges of wetlands, usually in the morning and late afternoon.
• Be ready for take-off and landing. Like this photograph, the most striking pictures often come as the bird opens its wings. Use a fast shutter speed so the wing feathers stay sharp, and keep the bird’s eye in focus.
• Use the sky with care. A bird against a bright sky can turn into a dark outline. Slight overexposure, or the camera’s exposure compensation, keeps detail in the darker wing feathers.
• Don’t use bait or calls, and never move branches or nesting material to get a clearer shot.
• Record what you see. Uploading sightings with dates and locations to eBird helps the data behind assessments like State of India’s Birds.

Conclusion

The Asian openbill is common in Assam, but its biology is unusual. The gap in its beak develops as it grows. The bird doesn’t use the gap to crack shells. It pulls snails out of them, possibly working largely by touch. Its numbers have risen in India’s farmland, though in some areas it is still hunted and its nesting trees are cut down. A single frame like this one from near Gohpur, of a bird landing high in a tree, shows the features that identify it: the spread black-and-white wings, the grey body, and the gap in the bill.