The lesser adjutant (Leptoptilos javanicus) is a large wading bird in the stork family Ciconiidae. Like other members of its genus, it has a bare neck and head. It is however more closely associated with wetland habitats where it is solitary and is less likely to scavenge than the related greater adjutant. It is a widespread species found from India through Southeast Asia.
Description
A large stork with an upright stance, a bare head and neck without a pendant pouch, it has a length of (outstretched from bill-to-tail measurement), weighs from and stands about tall. The only confusable species is the greater adjutant, but this species is generally smaller and has a straight upper bill edge (culmen), measuring in length, with a paler base and appears slightly trimmer and less hunch-backed. The skullcap is paler and the upper plumage is uniformly dark, appearing almost all black. The nearly naked head and neck have a few scattered hair-like feathers. The upper shank or tibia is grey rather than pink, the tarsus measures . The belly and undertail are white. Juveniles are a duller version of the adult but have more feathers on the nape. During the breeding season, the face is reddish and the neck is orange. The larger median wing coverts are tipped with copper spots and the inner secondary coverts and tertials have narrow white edging. The wing chord measures in length. Like others in the genus, they retract their necks in flight. In flight, the folded neck can appear like the pouch of the greater adjutant. Males and females appear similar in plumage but males tend to be larger and heavier billed.
Distribution and habitat
thumb|In Sri Lanka
The lesser adjutant is often found in large rivers and lakes inside well wooded regions, in freshwater wetlands in agricultural areas, and coastal wetlands including mudflats and mangroves. It is found in India, Nepal, Sri Lanka, Bangladesh (a colony with about 6 nests and 20 individuals was discovered near Thakurgaon in 2011), Myanmar, Thailand, Vietnam, Malaysia, Laos, Singapore, They are extremely rare in southern India. In Sri Lanka, they are found in lowland areas largely within protected areas, though they also use forested wetlands and crop fields.
Behaviour and ecology
The lesser adjutant stalks around wetlands feeding mainly on fish, frogs, reptiles, large invertebrates, rodents, small mammals and rarely carrion. Location of prey appears to be entirely visual, with one observation of storks sitting on telegraphic poles apparently scanning a marsh for prey.
Courtship behaviour of the lesser adjutant is identical to other species of the genus Leptoptilos. During pair formation, female birds lift their heads in a scooping motion with bill-clattering (called the "Balancing Posture"). Incubation period is 28–30 days. Another study the subsequent year across five locations along lowland Nepal monitored 65 colonies with 206 nests from which 280 chicks fledged, and the most frequently used tree species were B. ceiba, H. cordifolia and F. religiosa respectively. As of 2023, the global population is estimated to be 5,000–15,000 mature individuals.