Justification of Red List Category
This wide-ranging and long-lived species has a very small population which is declining very rapidly. For these reasons it is classified as Endangered.
The total population is estimated to number 800-1,200 mature individuals, roughly equivalent to 1,200-1,800 individuals in total. This is based on estimates of 650-800 birds in Assam, India, plus 150-200 birds in Cambodia, as well as at least 156 birds in Bihar state, India, which may have dispersed from the Assam population.
This species's population is suspected to be decreasing very rapidly, in line with levels of direct exploitation and habitat destruction, particularly lowland deforestation and the felling of nest-trees, and drainage, conversion, pollution and over-exploitation of wetlands. Given the species's longevity, population trends are measured over a three-generation period of 45 years and hence the impacts have been severe.
This species was previously widespread and common across much of South and continental South-East Asia but declined dramatically during the first half of the 20th century (Birdlife International 2001). It is known to breed in Assam (at least 650-800 birds, or more [Choudhury 2000]) and Bihar (more than 350 birds [A. Choudhury in litt. 2016]), India, and at the Tonle Sap lake (c.150 pairs [Visal and Mahood 2015]), Cambodia (T. Clements in litt. 2007). The species was reported to be breeding in Bihar, India, in 2004, and a small breeding population was discovered in the state on the Ganga and Kosi river floodplains in 2006 (Mishra and Mandal 2009). The population there appears to be increasing, with at least 156 estimated in 2008 and over 300 individuals in 2011, up from 78 in 2007 (Mishra and Mandal 2009, Kahn 2011). Kamrup District in Assam is known to be a stronghold for the species, with almost 75% of its population in Assam found in this district (Barman and Sharma in press). Recent records from Nepal, Bangladesh, and Thailand are presumed to refer to wanderers from India and Cambodia. Huge numbers once bred in Myanmar, but there have been just two recent reports from Meinmahla Kyun in 1998 and Kachin State in 2006 (G. Chunkino in litt. 2006). There are no confirmed records from Laos in recent years. Breeding success had been extremely poor in Assam with the number of nests in colonies declining sharply and for unknown reasons (Goswami and Patar 2006). However it is now considered to be breeding successfully in Assam with numbers increasing at a slow but steady rate (J. Mandal in litt. 2016). Large flocks of a few hundred birds are still noted around the city of Guwahati, which may provide feeding areas for around half of the species's world population (Choudhury 2008). Available data suggest that Cambodian populations declined heavily in the decades up to and including the 1990s. By 2001, several breeding sites recorded in the 1990s had been abandoned. Since 2001, protection measures were put in place at two known breeding sites (Prek Toal on the Tonle Sap and Kulen Promtep in Preah Vihear) which led to a stabilisation of national population declines and possible minor recoveries (Clements et al. 2007a,b). However the colony at Kulen Promtep is now extinct owing to forest clearance within the area (S. Mahood in litt. 2016).
While breeding in the dry season (October-April/May) it inhabits wetlands, nesting in tall trees with closed canopies and bamboo clumps around nesting trees, and historically on cliffs. Breeding is thought to coincide with the dry season in order to take advantage of abundant prey as water levels recede (Singha et al. 2003). In north-east India, it occurs close to and within urban areas (Barman and Sharma in press, A. Choudhury in litt. 2016), feeding around wetlands in the breeding season, and dispersing to scavenge at rubbish dumps, abattoirs and burial grounds at other times. In Cambodia, it breeds in freshwater flooded forest and areas of dry forest with ephemeral pools, otherwise dispersing to seasonally inundated forest, carcass dumps, tall wet grassland, mangroves and intertidal flats. It generally inhabits the lowlands but is occasionally found up to 1,500 m (Elliott and Kirwan 2016).
The key threats are direct exploitation, particularly at nesting colonies, habitat destruction, including felling of nest-trees, and drainage, conversion, pollution and over-exploitation of wetlands. Additionally, the Indian population is threatened by contaminated open rubbish dumps where pollutants are disposed along with carcasses and foodstuffs and it is also known to accidentally ingest polythene bags if food is wrapped inside (J. Mandal in litt. 2016). It has been suggested that recent nesting failures in Assam may be due to disease (Goswami and Patar 2006), which may have a negative impact upon the species in the future. Young birds may also become entangled in fishing nets and the species may suffer from the disturbance of arboreal animals, competition for nesting habitat from the Lesser Adjutant L. javanicus and the exacerbation of persecution levels owing to its pest status (Mishra and Mandal 2009). Poisoning of small wetlands to catch fish in the dry forests of northern and eastern Cambodia potentially poses a significant threat, and in Guwahati, India, pesticide use at open rubbish dumps where storks flocked to feed led to several mortalities in 2005. The population at Kulen Promtep Wildlife Sanctuary in the Northern Plains of Cambodia is now extinct owing to clearance of forest in the area (S. Mahood in litt. 2016). A major fire occurred in Prek Toal in early 2016. It is not yet known how this has impacted on the species (S. Mahood in litt. 2016).
Conservation Actions Underway
In Assam, it occurs in Kaziranga, Manas and Dibru-Saikhowa National Parks, and Pabitora, Deepor Beel, Laokhowa, Burhachapori and Pani-Dihing Sanctuaries (A. Choudhury in litt. 2016). Since 1991, there have been conservation awareness programmes in Assam. In Nagaon district, Assam, Green Guards (a local NGO) had a project to protect nesting trees and rehabilitate chicks fallen from nests but this has now stopped (A. Choudhury in litt. 2012). In Cambodia, the breeding colony at Prek Toal is a core area of the Tonle Sap Biosphere Reserve. Greater Adjutants historically bred at other sites on the Tonle Sap, but these colonies were abandoned by 2001. Conservation actions to reduce chick and egg collection and other forms of disturbance to the breeding colony at Prek Toal have been in place since the late 1990s, with permanent teams of protectors employed since 2001. Since 2001, c.95% of waterbird egg and chick collection has been prevented at Prek Toal. It is included in waterbird conservation awareness material in Laos and Cambodia. In Kamrup District, Assam a successful community conservation programme ran from 2009 to 2014 and during this period there were no records of nesting trees being cut down and the number of successful nests grew from 65 in 2010-2011 to 148 in 2013-2014 (Barman and Sharma in prep.).
145-150 cm. Huge, dark stork with very thick bill and pendulous neck-pouch. Pinkish naked head, white neck-ruff. Pale grey greater coverts and tertials contrasting with otherwise dark upperwing. Underwing-coverts paler than flight feathers. Juvenile has narrower bill than adult, denser head and neck-down and, initially, all dark wings. Similar spp. Lesser Adjutant L. javanicus is smaller, lacks neck pouch, has black greater coverts and tertials.
Text account compilers
Benstead, P., Bird, J., Butchart, S., Davidson, P., Peet, N., Pilgrim, J., Taylor, J., Tobias, J. & Ashpole, J
Choudhury, A., Chunkino, G., Clements, T., Htin Hla, T., Li, Z., Rahmani, A., Mandal, J. & Mahood, S.
BirdLife International (2020) Species factsheet: Leptoptilos dubius. Downloaded from http://www.birdlife.org on 09/08/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 09/08/2020.