Storm's Stork

The majority of the world population lives throughout the island of Borneo; occurring in Kalimantan (Indonesia), Swarak, Sabah (Malaysia) and Brunei. It is also found throughout Sumatra, although its range there was previously considered to be restricted to the south east. Despite being widespread on both of these islands, the population occurs at low densities and only one or a few individuals have ever been sighted together, with the largest number being 12 during an observation in Brunei. Smaller numbers live in some parts of peninsular Malaysia, where it appears to be particularly rare. An even smaller minority lives in the extreme south of Thailand, but this stork very unlikely occurs elsewhere in Thailand due to the near absence of remaining suitable habitat. In 1986, the first nest of this species ever known to science was discovered in Southern Thailand. However, the construction of the Chiew Larn Dam in the same year led to destruction of much of this stork's lowland forest habitat through extensive flooding. Following the flooding, Storm's stork was therefore believed to no longer breed there and since then was previously considered extinct in Thailand. However, this stork was re-sighted in Southern Thailand in 2004 with infrared camera traps; but continues to be exceptionally uncommon given that usually only one individual has been sighted at a time despite the high intensity of camera trapping. Nevertheless, its persistence in Southern Thailand does suggest the presence of a small breeding population. This stork's habitat is primarily dense lowland riverine forest and peat swamp forest, at altitudes not exceeding 240 metres above sea level. The density of large trees in this habitat exceeding 10 cm at breast height is estimated to range from 500 to 800 trees per hectare, and typical tree genera include Dipterocarpus and Ficus. The forest undergrowth predominantly comprises rattans, bamboos, shrubs and climbers. Because these habitats are largely inaccessible to humans, collecting data on this species is logistically difficult, which may partly explain why little is known about this stork's natural history. Although Storm's stork accepts both lowland riverine forest and peat swamp forest, it is currently unknown which of these habitats provide optimal living conditions for the species. However, peat-swamp forest does appear to be an underestimated, ecologically important habitat for this stork across much of its range. In the wake of continued anthropogenic loss of lowland riverine forest, peat-swamp forest possibly provides an important refuge for the species and an extensive area of peat swamp forest occurs in West Kalimantan. However, this forest habitat is also under threat through conversion to palm oil plantations, logging and forest fires, so that increased conservation efforts should be directed on protecting peat-swamp forest. This species has been shown to be somewhat tolerant of logged forests; however, these areas’ actual value as a breeding habitat for this species is disputed. Danielsen and Heegaard have considered Storm's stork incapable of breeding in logged forests despite apparent short term survival. In any case, current records have been too short to demonstrate long-term value of logged forests to this stork species. The acceptance of logged forests by Storm's stork may also entail some caveats; for example, that there must invariably be easy access within logged forest to freshwater margins, and that at least 20 years of forest regeneration should be allowed to elapse before real habitat value is re-established. A local mosaic of primary and logged forest may also explain this species’ apparent persistence in logged forest, because it may rely on the undisturbed forest patches as a refuge to sustain itself in the logged forest patches. This stork is often seen soaring at great heights over rivers and forest clearings, and like many other storks utilises thermals to assist it in gliding. This behaviour is said to be "contagious" because when one individual begins to soar, conspecifics join it in flight; with flocks consisting of up to six individuals. On Borneo, it has also been reported on open, grassy freshwater swamps and paddy fields. It appears to never frequent saline habitats, but occasionally uses forested inland areas adjacent to bodies of water subject to tidal movements and near mangrove swamps.

The population of this notably rare species has been thought to be in recent rapid decline, primarily due to clearance of its natural habitat to make way for oil palm plantations and logging activities. It has probably never been common, even before extensive habitat destruction from increased anthropogenic land exploitation. It has been classified as Endangered on the IUCN Red List since 1994. The total population has been estimated to number 400-500 wild individuals. Of these individuals, 150 are estimated to live in Malaysia; and an estimated 250 in Indonesia. This species is legally protected in Indonesia, Sarawak and Thailand. Although such protection has previously not been rigorously enforced, this stork has been recorded in numerous protected areas throughout its range, especially in Kalimantan, on Sumatra and in Malaysia. This species requires extensive areas of dense lowland forest over which to forage, so that the best solution to protect this species from extinction would be the large-scale establishment of protected areas holding undisturbed lowland forest and riparian features. However, because this stork is very secretive, it has proved difficult to investigate its biology and ecology. Although it is almost certainly negatively affected by deforestation, little continues to be known about the exact extent of its responses to anthropogenic changes in its native habitat.