Greater adjutants lack vocal muscles so they rely on unique behaviors and tactile forms of communication to interact with each other. Males often utilize beak clattering to advertise their territory and ward off other males. Males attract mates by presenting them with fresh twigs and later holding their beaks close to the female. Breeding pairs also perform head bobbing rituals that likely reinforce their pair-bond. Like all birds, greater adjutants perceive their environments through visual, auditory, tactile, and chemical stimuli.
Communication Channels: visual ; tactile ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
Many consider greater adjutants to be the most endangered stork in the world. Captive breeding programs have failed thus far, but efforts to protect natural habitats are active. Unfortunately, their tendency to nest near human settlements may prove fatal.
In the early part of the 20th century, the population size of greater adjutants is said to have numbered in the millions. They were common in Northern India, Bangladesh, Nepal and Southern Vietnam. Beginning in the mid 1980's the population began to decline heavily. Today an estimated 1,000 birds remain and likely breed only in the politically unstable Assam state of northern India. Populations are still declining and the IUCN red list lists greater adjutants as endangered.
Felling of large nesting trees, pollution of freshwater systems and a decline in the disposal of human corpses in public trash dumps are all thought to contribute to the rapid loss of this species. In Assam, recent reports of disease in this species also seems to be a contributing factor in its decline. Results of a survey of Assam residents revealed that only 30% of those polled knew greater adjutants are endangered. Greater community awareness of this unique species may help in its recovery.
CITES: no special status
IUCN Red List of Threatened Species: endangered
While greater adjutants pose no threat to humans they are often looked upon with disgust because of their general appearance, habit of defecating on their own legs, as well as diet of carrion.
Greater adjutants are valuable scavengers of discarded human waste, including unburied corpses as well as other large carrion. This service may have a role in preventing the spread of disease.
Greater adjutants are important scavengers of large carrion and likely contribute to sanitation and disease control in the environment. Like many birds, greater adjutants are hosts to avian lice including Colpocephalum cooki and Ciconiphilus temporalis.
Ecosystem Impact: biodegradation
Commensal/Parasitic Species:
In their native range, where they are primarily scavengers of large carrion, greater adjutants are known by the name "hargila," meaning bone swallower. They were once prevalent in Calcutta, where their tendency to consume human corpses left to rot in the streets was valued. One record indicates that a single greater adjutant effortlessly swallowed two buffalo vertebrae, measuring approximately 30 cm in length, in less than five minutes. Greater adjutants are most commonly found scavenging in mixed flocks near human garbage dumps or large carcasses. They can also be seen foraging independently near drying pools where they hunt insects, frogs, large fish, crustaceans and injured waterfowl. When foraging, greater adjutants use a method of tactile foraging where they hold their beaks open underwater and patiently wait for a prey item to swim between the open mandibles.
Animal Foods: birds; mammals; amphibians; fish; carrion ; insects; aquatic crustaceans
Primary Diet: carnivore (Scavenger )
Greater adjutants (Leptoptilos dubius) are exceedingly rare in their range from Northern India to Indochina and may breed exclusively in the Brahmaputra Valley of Assam. In the early part of the 20th century, large breeding populations of greater adjutants were common throughout Northern India, Bangladesh, Nepal and Southern Vietnam.
Biogeographic Regions: oriental (Native )
Greater adjutants (Leptoptilos dubius) have been observed in a variety habitats including marshes, lakes and jheels (shallow expansive lakes) as well as dry grasslands and fields. These birds are most frequently associated with slaughter houses and refuse sites near human settlements and were formerly common on the streets and rooftops of Calcutta. They typically nest in large trees and rock pinnacles near human settlements.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: savanna or grassland ; forest
Aquatic Biomes: lakes and ponds; temporary pools
Wetlands: marsh
Other Habitat Features: urban ; suburban ; riparian
Although the longest lifespan of a captive greater adjutant was 43 years, the longevity of these birds in the wild remains unknown.
Range lifespan
Status: captivity: 43 (high) years.
Greater adjutants are large birds, ranging in height from 120 to 152 cm with an impressive 250 cm wingspan. A long, thick yellow bill precedes the sparsely feathered, yellow to pink head and neck. The head is typically dappled with dark scabs of dried blood and characterized by the presence of a pendulous, inflatable gular pouch. The legs are naturally dark in color but frequently appear ashen due to regular defecation on the legs. When in flight, greater adjutants are recognizable by their white underside feathers and tendency to retract their necks like a heron. A mixture of white and gray feathers, which appear darker during the non-breeding season, adorn the rest of the body. Juvenile greater adjutants resemble adults, but have duller plumage and more feathers around the neck. The mass of these birds is unknown in the wild, but is estimated to be the heaviest of the storks.
Range length: 120 to 152 cm.
Average wingspan: 250 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike; ornamentation
No natural predators have been reported for this species. Unhealthy or young birds are likely preyed upon by local carnivores.
Other storks are known to be monogamous, but not always paired for life. It is thought that greater adjutants follow this mating system. Great adjutants are colonial nesters and will build many nests in the canopy of a single tree. Males claim suitable nesting branches and advertise their territory by perching on the branch with bills upward and exhibiting bill-clattering. When females perch nearby, males will present them with twigs as part of courtship. Courtship rituals consist more of courtship postures, where males will hold their beaks close to potential mates or tuck the females heads under their chins. Pairs also perform up-down bobbing motions together.
Greater adjutants nest in large, broad-limbed trees with sparse foliage. This choice of nesting tree is thought to facilitate landing and take-off for the large adult birds. Nests are constructed out of sticks and several pairs will often occupy the same tree. While females lay 3 eggs per season, an average of 2.2 chicks per pair are fledged successfully each year. Both parents participate in incubating eggs until they hatch after 28 to 30 days. Chicks fledge at 5 months of age.
Breeding interval: Greater adjutants breed once a year.
Breeding season: Greater adjtants breed during the dry season from October to June.
Average eggs per season: 3.
Range time to hatching: 28 to 30 days.
Average fledging age: 5 months.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; oviparous
Both male and female greater adjutants participate in nest building. After the eggs are laid, both parents also incubate the clutch for 28 to 30. The altricial chicks are cared for by both parents until they fledge at 5 months old.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Male, Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)
