Asian Openbill (Anastomus oscitans)

Asian Openbill (Anastomus oscitans)

The Asian Openbill (Anastomus oscitans) is a large wading bird belonging to the stork family (Ciconiidae). It is found primarily in the Indian subcontinent and Southeast Asia, including countries such as India, Nepal, Bangladesh, Myanmar, Thailand, Cambodia, Laos, and Vietnam. The Asian Openbill inhabits a variety of wetland habitats, such as marshes, swamps, rivers, and lakes, as well as flooded agricultural fields and rice paddies.

Physical Characteristics:

The Asian Openbill is a medium-sized stork, measuring approximately 68-81 centimeters (27-32 inches) in length, with a wingspan of around 149-156 centimeters (59-61 inches). The bird has a distinctive bill with a small gap, or “open bill,” between the upper and lower mandibles, which is an adaptation for feeding on its preferred prey. The plumage of the Asian Openbill is mostly greyish-white, with darker grey or black on the wings and tail. The legs and feet are also dark grey or black. Adults have a small, featherless patch of grey or pink skin around their eyes.


The primary food source for the Asian Openbill is freshwater snails, particularly the apple snail (Pomacea spp.), which is abundant in wetland habitats. The unique shape of the bird’s bill is perfectly adapted for extracting the snail from its shell. In addition to snails, the Asian Openbill may also consume other mollusks, crustaceans, insects, and small vertebrates such as fish and amphibians.

Reproduction and Lifecycle:

The breeding season for the Asian Openbill typically occurs during the rainy season when food is most abundant. These storks are colonial nesters, often building their nests in trees or bushes close to water. The nests are made of sticks and lined with grasses or leaves. Both the male and female participate in nest construction, incubation, and feeding of the chicks.

The female lays 2 to 4 white eggs, which are incubated by both parents for around 27-30 days. After hatching, the chicks are covered in white down and remain in the nest for about 35-40 days before fledging. The young birds reach sexual maturity at around 2-3 years of age.

Conservation Status:

The Asian Openbill is listed as “Least Concern” by the International Union for Conservation of Nature (IUCN), as it has a large range and a stable population. The species is not currently facing any significant threats. However, habitat loss due to wetland drainage and conversion to agricultural land, as well as pollution, could pose potential risks to the Asian Openbill population in the future.

Updated: 20 April 2023 — 14:09

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