Asian Openbill

Anastomus oscitans

The Asian Openbill is one of Bhigwan’s most distinctive birds — a large white stork that wades through the shallows with a bill that looks, from a distance, as if it has been broken. It has not. The gap is by design, and it makes this bird one of the most specialised feeders at the reservoir.

Status at Bhigwan: Resident & partial migrant
How often: Very common
Size: 68 cm
Family: Ciconiidae

Asian Openbill · Anastomus oscitans

How to identify it

The Openbill is unmistakable once you know what to look for. Stand at the water’s edge and scan the foraging flocks: the birds are white with black flight feathers and tail (juveniles are smoky brown, becoming whiter with each moult). The bill is stout and slightly decurved, but the diagnostic feature is the gap between the mandibles — the lower mandible bows downward in the middle so that even when the bill is shut, there is a clear space near the tip. Only at the very end do the mandibles meet, forming a gripping point.

In flight the Openbill soars on flat wings with the neck extended (unlike the Painted Stork, which shows a slight droop), and the black trailing edge and tail contrast cleanly with the white body.

Where & when to see it at Bhigwan

Asian Openbills are at Bhigwan year-round, but numbers swell in winter when birds from farther north move south. The flooded paddyfields west of the Kumbhargaon road and the shallow muddy arms of the reservoir — particularly where water is ankle-deep and apple snails (Pila globosa) are concentrated — hold the best feeding flocks. Groups of 20–100 birds are routine; after rains that inundate the surrounding fields, numbers can spike dramatically.

The birds roost communally in large trees at Kumbhargaon village. They return to the roost trees in the late afternoon and are noisy and active around them at dusk — a good spot for flight photography.

Field notes & behaviour

The entire bill structure is an adaptation for one food: large freshwater snails, particularly the apple snail Pila globosa. The bird wades slowly through shallow water, probing with its open bill. When a snail is felt, the mandibles close at the tip, gripping the shell. The bird then uses a twisting motion to extract the snail from its shell — the gap in the bill acts as a levering brace against the shell edge, preventing it from cracking before the snail is pulled free.

Young Openbills take months to master this technique. Fledglings at the reservoir margin can be watched attempting — and failing — to extract snails, trying different angles and grips until the action becomes efficient. It is one of the most observable examples of skill acquisition in Indian wildlife.

Photography tip

The golden hour after sunrise, when foraging birds are active in shallow water with the sun low behind you, gives the best light on the white plumage without blowing out. For flight shots at the roost, position yourself facing east at the roost trees in the late afternoon; birds returning over the darkening sky pick up the last warm light well. A shutter speed of at least 1/1600 sec freezes the large, slow wingbeats.

Similar species — don’t confuse it with…

The black-and-white patterning is shared with the Painted Stork and the Woolly-necked Stork, but neither has the Openbill’s distinctive bill gap. At range, the Openbill’s cleaner white-and-black pattern (no pink tertials, no woolly white neck) makes it straightforward.

Frequently asked questions

Why does the Openbill have a gap in its bill? +

The gap is a structural adaptation for handling large freshwater snails. The tip of the bill grips the snail’s body while the gap prevents the shell from being crushed — it acts as a brace. The bird then extracts the snail with a twisting pull. This specialisation means Openbills are entirely dependent on snail populations and follow their availability across the landscape.

Are Asian Openbills resident at Bhigwan or only winter visitors? +

Both. A resident breeding population nests colonially in trees near the reservoir, and additional birds from farther north swell the numbers in winter. After monsoon rains flood the surrounding fields, the local population is joined by large post-breeding flocks.