Thai National Parks

Birds of Thailand

Species of Thailand

Asian openbill

Binomial name: Anastomus oscitans, Pieter Boddaert, 1783

The Asian openbill or Asian openbill stork (Anastomus oscitans) is a large wading bird in the stork family Ciconiidae. This distinctive stork is found mainly in the Indian subcontinent and Southeast Asia. It is greyish white with glossy black wings and tail and the adults have a gap between the arched upper mandible and recurved lower mandible. Young birds are born without this gap which is thought to be an adaptation that aids in the handling of snails, their main prey. Although resident within their range, they make long distance movements in response to weather and food availability.

Description

The Asian openbill stork is predominantly greyish white with glossy black wings and tail that have a green or purple sheen. The name is derived from the distinctive gap formed between the recurved lower and arched upper mandible of the beak in adult birds. Young birds do not have this gap. The cutting edges of the mandible have a fine brush like structure that is thought to give them better grip on the shells of snails. The mantle is black and the bill is horn-grey. At a distance, they can appear somewhat like a white stork or Oriental stork. The short legs are pinkish to grey, reddish prior to breeding. Non-breeding birds have a smoky grey back instead of white. Young birds are brownish-grey and have a brownish mantle. Like other storks, the Asian openbill is a broad-winged soaring bird, which relies on moving between thermals of hot air for sustained flight. They are usually found in flocks but single birds are not uncommon. Like all storks, it flies with its neck outstretched. It is relatively small for a stork and stands at 68 cm height (81 cm long).

Habitat and distribution

The usual foraging habitats are inland wetlands and are only rarely seen along river banks and tidal flats. Birds may move widely in response to habitat conditions. Young birds also disperse widely after fledging. Individuals ringed at Bharatpur in India have been recovered 800 km east and a bird ringed in Thailand has been recovered 1500 km west in Bangladesh. Storks are regularly disoriented by lighthouses along the southeast coast of India on overcast nights between August and September. The species is very rare in the Sind and Punjab regions of Pakistan, but widespread and common in India, Sri Lanka, Burma and Thailand.

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 species, 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.

Breeding

The breeding season is after the rains, during July to September in northern India and November to March in southern India and Sri Lanka. They may skip breeding in drought years. The Asian openbill breeds colonially, building a rough platform of sticks often on half-submerged trees (often Barringtonia, Avicennia and Acacia species), typically laying two to four eggs. The nesting trees are shared with those of egrets, cormorants and darters. Nesting colonies are sometimes in highly disturbed areas such as inside villages. The nests are close to each other leading to considerable jostling among neighbours. Both parents take turns in incubation, the eggs hatching after about 25 days. The chicks emerge with cream coloured down and are shaded by the loosely outspread and drooped wings of a parent.

Like other storks, they are silent except for clattering produced by the striking of the male's bill against that of the female during copulation. They also produce low honking notes accompanied by up and down movements of the bill when greeting a partner arriving at the nest. Males may sometimes form polygynous associations, typically with two females which may lay their eggs in the same nest.

Relationship with other organisms

Young birds at the nest are sometimes preyed on by imperial, steppe and greater spotted eagles. Chaunocephalus ferox, an intestinal parasite, is a trematode worm found in about 80% of the wild populations in Thailand while another species Echinoparyphium oscitansi has been described from Asian openbills in Thailand. Other helminth parasites such as Thapariella anastomusa, T. oesophagiala and T. udaipurensis have been described from the oesophagus of storks.

This article uses material from Wikipedia released under the Creative Commons Attribution-Share-Alike Licence 3.0. Eventual photos shown in this page may or may not be from Wikipedia, please see the license details for photos in photo by-lines.

Videos of Asian openbill

  • Asian openbill - Bangkok

    Asian openbill - Bangkok

  • Asian openbill

    Asian openbill

  • Asian openbill

    Asian openbill

  • Asian Openbill

    Asian Openbill

Scientific classification

Kingdom
Animalia
Phylum
Chordata
Class
Aves
Order
Ciconiiformes
Family
Ciconiidae
Genus
Anastomus
Species
Anastomus oscitans

Conservation status

Least Concern (IUCN3.1)

Least Concern (IUCN3.1)

Distribution map of Asian openbill, Anastomus oscitans in Thailand
  • Ao Phang-Nga National Park
  • Ban Chang District, Rayong
  • Ban Laem District, Phetchaburi
  • Ban Lat District, Phetchaburi
  • Ban Lueam District, Nakhon Ratchasima
  • Ban Phai District, Khon Kaen
  • Ban Pho District, Chachoengsao
  • Ban Phraek District, Phra Nakhon Si Ayutthaya
  • Ban Sang District, Prachinburi
  • Bang Ban District, Phra Nakhon Si Ayutthaya
  • Bang Lamung District, Chonburi
  • Bang Pa In District, Phra Nakhon Si Ayutthaya
  • Bang Pahan District, Phra Nakhon Si Ayutthaya
  • Bang Pakong District, Chachoengsao
  • Bang Phra Non-hunting Area
  • Bang Pu Recreation Centre
  • Bang Saphan Noi District, Prachuap Khiri Khan
  • Bangkok Province
  • Borabue District, Maha Sarakham
  • Bueng Boraped Non-hunting Area
  • Chaiyo District, Ang Thong
  • Chatturat District, Chaiyaphum
  • Chiang Dao District, Chiang Mai
  • Chiang Dao Wildlife Sanctuary
  • Chiang Khong District, Chiang Rai
  • Chiang Saen District, Chiang Rai
  • Chum Ta Bong District, Nakhon Sawan
  • Doi Inthanon National Park
  • Doi Lo District, Chiang Mai
  • Doi Pha Hom Pok National Park
  • Doi Phu Kha National Park
  • Doi Saket District, Chiang Mai
  • Doi Tao District, Chiang Mai
  • Fang District, Chiang Mai
  • Hang Chat District, Lampang
  • Hat Noppharat Thara - Mu Ko Phi Phi National Park
  • Hat Yai District, Songkhla
  • Hua Hin District, Prachuap Khiri Khan
  • Huai Chorakhe Mak Reservoir Non-hunting Area
  • Huai Kha Khaeng Wildlife Sanctuary
  • Huai Krachao District, Kanchanaburi
  • Huai Talat Reservoir Non-hunting Area
  • Kabin Buri District, Prachinburi
  • Kaeng Khoi District, Saraburi
  • Kaeng Krachan District, Phetchaburi
  • Kaeng Krachan National Park
  • Kanthararom District, Sisaket
  • Kantharawichai District, Maha Sarakham
  • Khanom District, Nakhon Si Thammarat
  • Khao Ang Rue Nai Wildlife Sanctuary
  • Khao Chong
  • Khao Dinsor (Chumphon Raptor Center)
  • Khao Laem National Park
  • Khao Luang National Park
  • Khao Nang Panthurat Forest Park
  • Khao Phra - Bang Khram Wildlife Sanctuary
  • Khao Sam Roi Yot National Park
  • Khao Sanam Prieng Wildlife Sanctuary
  • Khao Sok National Park
  • Khao Yai National Park
  • Khao Yoi District, Phetchaburi
  • Khlong Lan National Park
  • Khuan Khanun District, Phatthalung
  • Khun Chae National Park
  • Khun Tan District, Chiang Rai
  • Khura Buri District, Phang Nga
  • Klaeng District, Rayong
  • Ko Sichang District, Chonburi
  • Ko Tao
  • Kui Buri National Park
  • Kumphawapi District, Udon Thani
  • Kut Thing Non-hunting Area
  • Laem Pak Bia
  • Mae Ai District, Chiang Mai
  • Mae Chan District, Chiang Rai
  • Mae Mo District, Lampang
  • Mae Rim District, Chiang Mai
  • Mae Taeng District, Chiang Mai
  • Mae Tha, Lampang District, Lampang
  • Mae Wong National Park
  • Mu Ko Similan National Park
  • Mueang Buriram District, Buriram
  • Mueang Chachoengsao District, Chachoengsao
  • Mueang Chaiyaphum District, Chaiyaphum
  • Mueang Chiang Mai District, Chiang Mai
  • Mueang Chiang Rai District, Chiang Rai
  • Mueang Chonburi District, Chonburi
  • Mueang Kalasin District, Kalasin
  • Mueang Kamphaeng Phet District, Kamphaeng Phet
  • Mueang Kanchanaburi District, Kanchanaburi
  • Mueang Khon Kaen District, Khon Kaen
  • Mueang Krabi District, Krabi
  • Mueang Lampang District, Lampang
  • Mueang Lopburi District, Lopburi
  • Mueang Maha Sarakham District, Maha Sarakham
  • Mueang Nakhon Nayok District, Nakhon Nayok
  • Mueang Nakhon Ratchasima District, Nakhon Ratchasima
  • Mueang Nakhon Si Thammarat District, Nakhon Si Thammarat
  • Mueang Pattani District, Pattani
  • Mueang Phang Nga District, Phang Nga
  • Mueang Phatthalung District, Phatthalung
  • Mueang Phetchabun District, Phetchabun
  • Mueang Phetchaburi District, Phetchaburi
  • Mueang Phichit District, Phichit
  • Mueang Phitsanulok District, Phitsanulok
  • Mueang Phuket District, Phuket
  • Mueang Ratchaburi District, Ratchaburi
  • Mueang Rayong District, Rayong
  • Mueang Sa Kaeo District, Sa Kaeo
  • Mueang Saraburi District, Saraburi
  • Mueang Satun District, Satun
  • Mueang Songkhla District, Songkhla
  • Mueang Sukhothai District, Sukhothai
  • Mueang Suphanburi District, Suphan Buri
  • Mueang Surat Thani District, Surat Thani
  • Mueang Surin District, Surin
  • Mueang Tak District, Tak
  • Mueang Udon Thani District, Udon Thani
  • Mueang Uttaradit District, Uttaradit
  • Non Thai District, Nakhon Ratchasima
  • Nong Bong Khai Non-hunting Area
  • Nong Han Lake
  • Nong Song Hong District, Khon Kaen
  • Nong Thung Thong Non-hunting Area
  • Nong Waeng Non-hunting Area
  • Nong Ya Plong District, Phetchaburi
  • Nong Yai Area Development Project Under Royal Init
  • Pa Sak Chonlasit Dam Non-hunting Area
  • Pai District, Mae Hong Son
  • Pak Chong District, Nakhon Ratchasima
  • Pak Phli District, Nakhon Nayok
  • Pak Thale
  • Pak Tho District, Ratchaburi
  • Pak Thong Chai District, Nakhon Ratchasima
  • Pang Sila Thong District, Kamphaeng Phet
  • Pha Nam Yoi Forest Park
  • Phaisali District, Nakhon Sawan
  • Phan District, Chiang Rai
  • Phanat Nikhom District, Chonburi
  • Phatthana Nikhom District, Lopburi
  • Phayuha Khiri District, Nakhon Sawan
  • Phimai District, Nakhon Ratchasima
  • Pho Prathap Chang District, Phichit
  • Phra Nakhon Si Ayutthaya District, Phra Nakhon Si Ayutthaya
  • Phra Phrom District, Nakhon Si Thammarat
  • Phu Hin Rong Kla National Park
  • Phu Langka National Park
  • Phunphin District, Surat Thani
  • Pran Buri District, Prachuap Khiri Khan
  • Pran Buri Forest Park
  • Sai Yok District, Kanchanaburi
  • Sakaerat Environmental Research Station
  • Salak Pra Wildlife Sanctuary
  • Samut Prakan Province
  • San Sai District, Chiang Mai
  • Sanam Bin Reservoir Non-hunting Area
  • Sanam Chai Khet District, Chachoengsao
  • Sankhaburi District, Chainat
  • Santi Suk District, Nan
  • Sathing Phra District, Songkhla
  • Sattahip District, Chonburi
  • Satuek District, Buriram
  • Si Maha Phot District, Prachinburi
  • Si Racha District, Chonburi
  • Si Satchanalai District, Sukhothai
  • Song Phi Nong District, Suphan Buri
  • Sri Nakarin Dam National Park
  • Ta Phraya National Park
  • Takua Pa District, Phang Nga
  • Taphan Hin District, Phichit
  • Tha Sala District, Nakhon Si Thammarat
  • Tha Takiap District, Chachoengsao
  • Tha Wung District, Lopburi
  • Tha Yang District, Phetchaburi
  • Thalang District, Phuket
  • Thale Noi Non-hunting Area
  • Tham Pratun Non-hunting Area
  • Than Sadet - Koh Pha-Ngan National Park
  • Thap Lan National Park
  • Thawat Buri District, Roi Et
  • Wang Chan District, Rayong
  • Wang Nam Yen District, Sa Kaeo
  • Wang Noi District, Phra Nakhon Si Ayutthaya
  • Watthana Nakhon District, Sa Kaeo
  • Yang Talat District, Kalasin

Range map of Anastomus oscitans in Thailand

Important note; our range maps are based on limited data we have collected. The data is not necessarily accurate or complete.

Special thanks to Ton Smits and Parinya Pawangkhanant for their help with many range data.

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