Milky Stork

During high tide, individuals often roost in mangrove trees or in remnant trees on rice fields. Roosting also occurs in crowns of tall mangrove trees and on the ground on intertidal mudflats and marshes. Between foraging activities, individuals have been observed standing in shaded spots or in the sun adopting a wings drooped position. Common comfort movements in the milky stork include allopreening between breeding partners and head shaking. Individuals perched near incubating partners also carrying out head rubbing, whereby the stork oils the bare head skin on its preen gland and then rubs its head on its plumage.

The milky stork's range is restricted to Southeast Asia, where it is widely but patchily distributed. It occurs in Sumatra (its global stronghold), Java, Sulawesi, eastern Malaysia, Cambodia, southern Vietnam (where it probably largely recolonised after the war of 1963–75), Bali, Sumbawa, Lombok and Buton. It historically occurred in southern Thailand, but is now very likely extinct here. One perfect adult male milky stork specimen from Setul in Peninsula Thailand taken from 1935 was later found among collections of the Zoological Reference Collection at the National University of Singapore, suggesting that the species was formerly resident here. The discovered specimen was the first, and probably also the last milky stork to be reported from Thailand, although this stork probably still occasionally visits Thailand as a vagrant. It is also vagrant elsewhere to countries such as Bali and Sumbawa, and is resident on Sumatra, Java and Sulawesi (all within Indonesia). The milky stork was first reported on Sulawesi when a group of five apparently resident individuals was sighted there in 1977. The island of Madura may also support an important population after 170 individuals were sighted there in 1996. The milky stork previously ranged more widely throughout Southeast Asia. For example, it was formerly widely distributed along the coasts of the Malaysian Peninsula, but is now restricted to Matang Mangrove Forest in Perak. The milky stork is predominantly a lowland coastal species throughout its range; where it inhabits mangrove, freshwater and peat swamps, and estuaries. The only proven breeding records however are reported from mangroves bordering the feeding grounds. It forages on tidal mudflats, in shallow saline or freshwater pools, freshwater marshes, fishponds, rice fields; and on backswamps along river floodplains up to 15 km from the coast. The milky stork's breeding habitat requirements are extensive and undisturbed mangrove (and probably also riverine or dryland) forest with tall, outstanding trees behind it; and shallow pools within the forest for juveniles to forage in. The tall trees are also used for resting, and there should be sufficient individual limbs from which to take off. With a lack of such suitable trees, manmade alternatives such as cart wheels mounted on poles have been proposed. In Peninsula Malaysia, the milky stork is more exclusively marine than the congeneric painted stork. However, the two species’ ranges are said to overlap in the marshy plains of Cambodia, where they probably use the same habitats.

In 2008, the global population was fewer than 2200 individuals, which is a reduction from approximately 5000 in the 1980s. In Malaysia, population counts decreased steadily from over 100 individuals in 1984 to less than 10 by 2005 (by over 90%), so that the population here faces local extinction. Of the current world population estimate, there are probably about 1600 individuals in Sumatra, less than 500 on Java, and less than 100 on the southeast Asian mainland. The Cambodian population is very small, numbering 100–150 individuals; and although it may be relatively stable, rapid declines are expected if serious threats persist. Due to the substantial population declines across its range, the milky stork's population status was elevated to Endangered from Vulnerable in 2013 by the IUCN.