Giant Ibis
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The giant ibis (''Pseudibis gigantea'') is a wading
bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...
of the
ibis The ibis () (collective plural ibises; classical plurals ibides and ibes) are a group of long-legged wading birds in the family Threskiornithidae that inhabit wetlands, forests and plains. "Ibis" derives from the Latin and Ancient Greek word f ...
family,
Threskiornithidae The family Threskiornithidae includes 36 species of large wading birds. The family has been traditionally classified into two subfamilies, the ibises and the spoonbills; however, recent genetic studies have cast doubt on this arrangement, and ha ...
. It is confined to northern Cambodia, with a few birds surviving in extreme southern Laos and a recent sighting in Yok Đôn National Park, Vietnam. It is sometimes placed in the genus ''Thaumatibis''.


Description

True to its name, it is the largest extant ibis species. Adults are long and weigh about . Among standard measurements, the wing chord is , the
tail The tail is the elongated section at the rear end of a bilaterian animal's body; in general, the term refers to a distinct, flexible appendage extending backwards from the midline of the torso. In vertebrate animals that evolution, evolved to los ...
is , the tarsus is and the culmen is . The adults have overall dark grayish-brown plumage with a naked, greyish head and upper neck. There are dark bands across the back of the head and shoulder area and the pale silvery-grey wing tips also have black crossbars. The beak is yellowish-brown, the legs are orange, and the eyes are dark red. Juveniles have short black feathers on the back of the head down to the neck, shorter bills and brown eyes. It has a loud, ringing call, frequently repeated around dawn or dusk, ''a-leurk a-leurk''.


Distribution and habitat

The giant ibis is a lowland bird that occurs in
marsh In ecology, a marsh is a wetland that is dominated by herbaceous plants rather than by woody plants.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p More in genera ...
es,
swamp A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...
s,
lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...
s, wide
river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...
s, flooded
plain In geography, a plain, commonly known as flatland, is a flat expanse of land that generally does not change much in elevation, and is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains, as coastal plains, and ...
s and semi-open
forest A forest is an ecosystem characterized by a dense ecological community, community of trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, ...
s as well as pools, ponds and seasonal water-meadows in denser
deciduous forest In the fields of horticulture and botany, the term deciduous () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed leaves, usually in the autumn; to the shedding of petals, after flo ...
. It generally is found in lowlands. One bird was collected in a Malay paddyfield. Formerly the giant ibis was believed to breed in eastern Thailand, central and northern Cambodia, southern Laos and southern Vietnam. It was still fairly common in the
Mekong Delta The Mekong Delta ( or simply ), also known as the Western Region () or South-western region (), is the list of regions of Vietnam, region in southwestern Vietnam where the Mekong, Mekong River River delta, approaches and empties into the sea th ...
until the 1920s but is now almost depleted, with a small remnant population breeding in Cambodia, southern Laos and possibly in Vietnam.


Behaviour and ecology


Food and feeding

The giant ibis eats aquatic
invertebrate Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...
s,
eel Eels are ray-finned fish belonging to the order Anguilliformes (), which consists of eight suborders, 20 families, 164 genera, and about 1000 species. Eels undergo considerable development from the early larval stage to the eventual adult stage ...
s,
crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...
s and small
amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...
s and
reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...
s.
Insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...
s such as
locust Locusts (derived from the Latin ''locusta'', locust or lobster) are various species of short-horned grasshoppers in the family Acrididae that have a swarming phase. These insects are usually solitary, but under certain circumstances they b ...
s and
cicada The cicadas () are a superfamily, the Cicadoidea, of insects in the order Hemiptera (true bugs). They are in the suborder Auchenorrhyncha, along with smaller jumping bugs such as leafhoppers and froghoppers. The superfamily is divided into two ...
s are eaten regularly when abundant and
seed In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds ...
s occasionally supplement the diet. Outside of the breeding season,
frog A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order (biology), order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough ski ...
s and mole-crickets appear to be perhaps the most significant prey types for giant ibises. They mainly forage in muddy substrate in shallow waters, though can feed at all depths in seasonal forest pools. Feeding flocks may consist of a breeding pair or small family group and have been observed mixing with black ibises.


Breeding

Next to nothing is known of its breeding behaviour, but it nests in
tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, e.g., including only woody plants with secondary growth, only ...
s, with a possible preference for ''
Dipterocarpus '' D. retusus'' in Köhler ''Dipterocarpus'' is a genus of flowering plants and the type genus of family Dipterocarpaceae. ''Dipterocarpus'' is the third-largest and most diverse genus among the Dipterocarpaceae. The species are well known for ...
'' trees. Usually, nests are located at least from human habitations, although the species is not especially shy around or fearful of humans unless persistently harassed or hunted. Females lay two eggs at the start of the rainy season, around June to September.
Earthworm An earthworm is a soil-dwelling terrestrial invertebrate that belongs to the phylum Annelida. The term is the common name for the largest members of the class (or subclass, depending on the author) Oligochaeta. In classical systems, they we ...
s taken from their mounds in wet grasslands appears to be an important food source for nesting ibises of this species. In general, the species is residential but can wander widely for food or in response to disturbances. The giant ibis is generally territorial and may remain with a family group throughout the year. However, in the dry season, when they are not nesting, groups of up to seven individuals, sometimes likely unrelated, have been observed feeding together.


Status

The giant ibis is considered to be
Critically Endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...
on the
IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is an inventory of the global conservation status and extinction risk of biological ...
. The primary causes seem to be drainage of wetlands for cultivation and the epidemic clear-cutting of forest for rubber, cassava, wood pulp and teak plantations in south-east Asia. Habitats may also face ravaging due to local human warfare. Increasing human populations in Cambodia have in turn lead to disturbance and further lowland
deforestation Deforestation or forest clearance is the removal and destruction of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. Ab ...
. The ibis may be hunted for meat by people and eggs may be predated by the
Asian palm civet The Asian palm civet (''Paradoxurus hermaphroditus''), also called common palm civet, toddy cat and musang, is a viverrid native to South and Southeast Asia. Since 2008, it is IUCN Red Listed as Least Concern as it accommodates to a broad range o ...
and the
yellow-throated marten The yellow-throated marten (''Martes flavigula'') is a marten species native to the Himalayas, Southeast Asia, Southeast and East Asia. Its coat is bright yellow-golden, and its head and back are distinctly darker, blending together black, white, ...
, with the species certainly unable to withstand sustained predation. A reduction in seasonal pools in forest, previously made by now depleted populations of
megafauna In zoology, megafauna (from Ancient Greek, Greek μέγας ''megas'' "large" and Neo-Latin ''fauna'' "animal life") are large animals. The precise definition of the term varies widely, though a common threshold is approximately , this lower en ...
(especially
wild Asian water buffalo The wild water buffalo (''Bubalus arnee''), also called Asian buffalo, Asiatic buffalo and wild buffalo, is a large bovine native to the Indian subcontinent and Southeast Asia. It has been listed as ''Endangered'' in the IUCN Red List since 19 ...
), may also negatively effect them. Local droughts, possibly related to
global climate change Present-day climate change includes both global warming—the ongoing increase in global average temperature—and its wider effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes ...
, have appeared to have further compromised the breeding habitat and behaviour of the species. Some conservation efforts have been undertaken, including protecting nests by the installation of metal belts that prevent predators from accessing them, but the protection of ideal habitat and the increasing human populations in Cambodia continues to be a vexing challenge. Increasing
ecotourism Ecotourism is a form of nature-oriented tourism intended to contribute to the Ecological conservation, conservation of the natural environment, generally defined as being minimally impactful, and including providing both contributions to conserv ...
in the region and education to local people is clearly required for the species to successfully recover from the brink of extinction. The current population is estimated at 100 pairs, with a total population (including young and juveniles) of fewer than 500 individuals. However, even these figures may be optimistic. In 2018 the
IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...
stated there were less than 200 mature individuals in the population.


References

*Hancock & Kushan, ''Storks, Ibises and Spoonbills of the World''. Princeton University Press (1992), .


External links


BirdLife species factsheet.

ARKive pics and videos
{{Taxonbar, from=Q931759 Threskiornithidae Birds of Southeast Asia Birds of Laos Birds of Cambodia Birds of Vietnam Birds described in 1877 Ibises Taxa named by Émile Oustalet National symbols of Cambodia