20-12-2015 JURONG, SINGAPORE - AMERICAN FLAMINGO (Phoenicopterus ruber)

The American flamingo (Phoenicopterus ruber) is a large species of flamingo native to the Neotropics. It is the only flamingo that naturally inhabits North America.

The American flamingo is a large wading bird. Most of its plumage is pink, giving rise to its earlier name of Rosy flamingo and differentiating adults from the much paler Greater flamingo. The wing coverts are red, and the primary and secondary flight feathers are black. The bill is pink and white with an extensive black tip. The legs are entirely pink. Adult American flamingos are smaller on average than Greater flamingos but are the largest flamingos in the Americas.

The American flamingo inhabits South America’s north coast, the Yucatan Peninsula in Mexico, and some of the Caribbean islands. There is also a small isolated population that inhabits the Galapagos Islands. It is the only flamingo that is native to North America. It lives in a wide variety of freshwater and saline habitats such as lagoons, estuaries, coastal and inland lakes, and mudflats.

American flamingos are threatened by human disturbance and habitat loss along the Caribbean’s coastal wetlands.

IUCN Red List estimates the number of mature individuals to be around 260,000-330,000 birds. Overall, the numbers of this species are increasing today, and it is classified as least concern (LC).

American flamingos eat large amounts of crustaceans, aquatic invertebrates, and algae, and so have a big impact on these populations.

Flamingos live, feed, and breed in large flocks, which may number thousands of individuals. When mating and interacting with others in the colony, they use highly ritualized displays. Most of the day American flamingos spend feeding. They are shy and fly away if disturbed. Both adults and juveniles spend most of their time feeding, preening, and resting. Each individual becomes aggressively territorial when foraging for food. A bird claims a "territory" and doesn’t allow others to come nearby. If one does come too close, the bird that has been offended will exhibit threatening displays in warning, so that the intruder will leave. A colony establishes distinct areas where the birds can freely interact, the drinking area being one such place. Like other flamingo species, American flamingos will migrate short distances to ensure that they get enough food or because their current habitat has been disturbed in some way. While their flights are not as long as other migratory birds, flamingos still fly for periods without eating.

American flamingos are monogamous, with strong, long-term pair bonds. They engage in group courtship displays, thousands of birds turning their heads, bowing their necks, or raising their wings in spectacular synchrony. These displays make sure that the colony members are all ready for mating at the same time. These birds mate after the rainy season, typically in spring or summer. The parents both build the nest. Usually, just one egg is laid and is incubated by the male and the female for 27 to 31 days. Both parents feed the chick, with the typical “crop milk” that is secreted in the adults’ upper digestive tract. The chick is brooded for about 5-15 days, and then it gathers with other chicks in large crèches which several adults look after. It fledges at about 70-75 days old and becomes reproductively mature when it is 3-5 years old.

20-12-2015 JURONG, SINGAPORE - EURASIAN GREAT CORMORANT (Phalacrocorax carbo)

The Great cormorant (Phalacrocorax carbo) is a widespread member of the cormorant family of seabirds. Many fishermen see in the Great cormorant a competitor for fish. Because of this, it was hunted nearly to extinction in the past but luckily due to conservation efforts, its numbers increased.

The Great cormorant is a large black bird, but there is a wide variation in size in the species' wide range. Males are typically larger and heavier than females. It has a longish tail and yellow throat patch. Adults have white patches on the thighs and on the throat in the breeding season. In European waters, the Great cormorant can be distinguished from the Common shag by its larger size, heavier build, thicker bill, lack of a crest, and plumage without any green tinge. In eastern North America, it is similarly larger and bulkier than the Double-crested cormorant, and the latter species has more yellow on the throat and bill and lack the white thigh patches frequently seen on great cormorants.

Great cormorants occur throughout Europe, Asia, Australia, Africa, and northeastern coastal North America. They may be both resident and migratory. Throughout the year in some areas, large groups remain within the breeding range. Greta cormorants frequent open marine environments and inland waters. They inhabit sandy or rocky sheltered coasts and estuaries and are rarely seen any distance from the coast. This species breeds on cliffs and inshore islands, among boulders and man-made structures. Birds that nest inland will breed on trees, bushes, and reedbeds, and even on bare ground.

Great cormorants are active during the day and are social birds, usually leaving roosts to forage early in the morning and returning within an hour. Little time each day is spent foraging, although parents with young tend to forage for longer. Much of the day is spent resting and preening near foraging areas or at roosts. Great cormorants generally are not aggressive towards one another, apart from at nest sites, where they exhibit territorial behavior. There may be dominance hierarchies. Outside of the breeding season, they usually gather in mixed-age, mixed-sex groups.

Great cormorants are monogamous, with pairs sometimes reuniting in subsequent years. The male chooses the nest site, displaying to attract the female by waving his wings up and down and flashing his white rump patch. He will also swing his head from side to side while holding his tail erect and calling loudly. The female responds by swinging her head slightly and “purring”. This species breeds at any time, depending on food resources. Breeding takes place in colonies of as many as 2,000 pairs, although colonies of a smaller size are typical. Colonies are often located close to other species, like darters, herons, and spoonbills. The parents build their nest with reeds, sticks, and seaweeds on a cliff, in a tree, or in a bush, according to the region. Often a nest is reused. 2 to 6 eggs are laid, with an average of 3-4. The parents share the incubation for 27 to 31 days. The altricial chicks hatch at intervals and fledge at about 50 days old. They remain with their parents for 50 or more days, relying on them for food. The young start to breed between 2 and 4 years old, typically when 3 years old.

20-12-2015 JURONG, SINGAPORE - GOLDEN PHEASANT (FEMALE) (Chrysolophus pictus)

The Golden pheasant (Chrysolophus pictus) is a colorful bird native to forests in mountainous areas of China. The genus name of this bird comes from Ancient Greek khrusolophos which means "with golden crest", and pictus - Latin for "painted" from pingere, "to paint".

The adult male of this species is unmistakable with its golden crest and rump and bright red body. The deep orange "cape" can be spread in display, appearing as an alternating black and orange fan that covers all of the face except its bright yellow eye with a pinpoint black pupil. The female is much less showy, with a duller mottled brown plumage. The female's breast and sides are barred buff and blackish brown, and the abdomen is plain buff. She has a buff face and throat. Some abnormal females may later in their lifetime get some male plumage. Both males and females have yellow legs and yellow bills.

Golden pheasants are found in western China. They prefer dense conifer forests in mountainous regions but can also be found in mixed forests with thick shrubs.

Golden pheasants are sedentary and generally solitary birds; outside of the breeding season, they prefer to stay singly. These are mainly terrestrial birds. While they can fly clumsily in short bursts, they prefer to run and spend most of their time on the ground. They feed on the ground but roost in trees at night. During winter, flocks often forage close to human settlements at the edge of the forest, taking primarily wheat leaves and seeds. If startled, they can suddenly burst upwards at great speed and with a distinctive wing sound. Golden pheasants communicate with a wide range of calls that are used in different situations. Their main call sounds as 'chack chack' and in the breeding season males produce a metallic call.

20-12-2015 JURONG, SINGAPORE - JAVAN MYNA (Acridotheres javanicus)

The Javan myna (Acridotheres javanicus ), also known as the white-vented myna, is a species of myna. It is a member of the starling family. It is native to Bali and Java. It has been introduced to other Asian countries, and as far away as Puerto Rico.

The Javan myna is mainly black. The wings are brownish-black, and the primaries have white bases. The undertail-coverts are white. There is a short crest on the forehead.Its beak, legs and feet are yellow. The eyes are lemon-yellow. The immature is browner. Its length is 21–23 cm (8.3–9.1 in). Its weight is about 100 g (3.5 oz).

The Javan myna is omnivorous and eats seeds, fruit, nectar, insects and human waste. It is often found in large groups. Its voice is similar to that of the common myna. It builds its nest in holes. The eggs are bluish-glaucous. Javan mynas are bold and not very afraid of humans. Javan mynas are kept in cages in Malaysia and Indonesia. The birds scavenge in groups, minimum two but usually three or more, with all except one feeding and one usually at a vantage point keeping a look out. If the bird that is keeping watch sees anything that might pose a threat, it alarms the group members with a high pitch tweet and they all flee the area swiftly.

20-12-2015 JURONG, SINGAPORE - WHITE NAPED CRANE (Antigone vipio)

These cranes breed in northeastern China, northeastern Mongolia, and adjacent parts of southeastern Russia. Individuals in the western part of the breeding range will migrate south through China, stopping to rest at the Yellow River delta, then wintering in wetlands of the middle Yangtze River valley. Overwintering areas include the Demilitarized Zone that separates North and South Korea, as well as the Japanese island Kyushu, where there is an artificial feeding station outside the city of Izumi which they heavily rely upon. These birds prefer shallow wetlands or wet meadows within broad river valleys, near lake edges, and within lowland steppes or areas that are mixed forest-steppe. They feed nest, and roost in shallow wetlands and along the edges of wetlands, foraging in the adjacent grasslands or farmlands. While migrating and at their wintering grounds, they will use rice paddies, agricultural fields, mudflats, and other wetlands.

The White-naped crane is a social bird and is often found alongside other crane species within their range, such as Red-crowned, Hooded, Eurasian and Demoiselle cranes. A White-naped crane is diurnal and when foraging it digs into the soil with its long bill, to reach tubers and roots. This species is fairly territorial when digging and feeding. As with all cranes species, these cranes are often observed ‘dancing’: flapping their wings, tossing sticks and grass, jumping, running and bowing. These actions are part of courtship, but are also thought to relieve tension and reduce aggression. White-naped cranes start a flight by running along the ground, and taking off into the wind, quickly gaining speed, and lifting into the air, to fly with outstretched necks, while the legs trail behind. They use thermal currents whenever possible. They fly in a V formation during migration. They make high-pitched, penetrating calls.

20-12-2015 JURONG, SINGAPORE - GOLDEN BACKED WEAVER (Ploceus jacksoni)

https://www.inaturalist.org/taxa/13835-Ploceus-jacksoni

27-12-2015 SAIGON, VIETNAM - GREY HEADED SWAMPHEN (Porphyrio poliocephalus)

The grey-headed swamphen (Porphyrio poliocephalus ) is a species of swamphen occurring from the Middle East and the Indian subcontinent to southern China and northern Thailand. It used to be considered a subspecies of the purple swamphen, but was elevated to full species status in 2015; today the purple swamphen is considered a superspecies and each of its six subspecies groups are designated full species.

The male has an elaborate courtship display, holding water weeds in his bill and bowing to the female with loud chuckles.

The grey-headed swamphen was introduced to North America in the late 1990s due to avicultural escapes in the Pembroke Pines, Florida area. State wildlife biologists attempted to eradicate the birds, but they have multiplied and can now be found in many areas of southern Florida. Ornithological authorities consider it likely that the swamphen will become an established part of Florida's avifauna. It was added to the American Birding Association checklist in February 2013.

Looking like an oversized version of a Purple Gallinule with a massive red bill, the Gray-headed Swamphen is an impressive bird and the largest rail in North America. Originally from southern Asia, it became established in southern Florida in the mid-1990s when birds escaped from captivity and began breeding. Like gallinules, this species forages in marshes by wading, swimming, and even climbing to reach aquatic vegetation, insects, and animal prey. Swamphens are aggressive competitors and may dominate or displace our native North American rails.

27-12-2015 SAIGON, VIETNAM - PAINTED STORK (Mycteria leucocephala)

27-12-2015 SAIGON, VIETNAM - MARABOU STORK (Leptoptilos crumenifer)

The Marabou stork (Leptoptilos crumenifer) is a large wading bird that breeds in Africa often near human habitation, especially landfill sites. It is sometimes called the "undertaker bird" due to its shape from behind: cloak-like wings and back, skinny white legs, and sometimes a large white mass of "hair".

Marabou storks are scavengers and feed mainly on carrion. However, they occasionally eat other birds including pigeons, doves, pelican and cormorant chicks, and even flamingos. During the breeding season, adult marabous take mostly small, live prey since nestlings need this kind of food to survive. Common prey at this time may consist of fish, frogs, insects, eggs, small mammals, and reptiles such as crocodile hatchlings and eggs, and lizards and snakes.

The Marabou stork is a massive bird. This bird is unmistakable due to its size, bare head, and neck, huge bill, pink gular sac at its throat (crumenifer(us) - means "carrier of a pouch for money"), and neck ruff. The male and the female are alike, but the young bird is browner and has a smaller bill.

Marabou storks breed in Africa south of the Sahara. They live in both wet and arid habitats and can be found in open dry savannas, grasslands, riverbanks, lakeshores, and swamps. These birds are also frequent visitors to landfills and fishing villages.

Marabou storks are monogamous and form strong pair bonds that last for life. They breed in colonies, starting during the dry season when food is more readily available as the pools shrink. Males attract a female with bill-rattling courtship displays and their throat sac is also used to make various noises at that time. Marabous build a small nest in a tree made of sticks and line it with twigs and green leaves. The female lays 2-3 eggs which hatch after an incubation period of 30 days. At hatching, the chicks are fed by both parents and fledge between 13 and 15 weeks of age. They remain with their parents for about another 4 months and reach reproductive maturity at 4 years of age.

Marabou storks are social birds and often gather in groups near lakes or rivers. They are generally silent but may sometimes make grunts, croak with their throat sac, or rattle their bills. These large and powerful birds eat mainly carrion, scraps, and feces but will opportunistically eat almost any animal matter they can swallow. Marabou storks feed by day soaring high over the open country looking for food or frequently following vultures which lead them to carrion. When feeding on carrion, marabous may wait for the vultures to cast aside a piece, steal a piece of meat directly from the vulture or wait until the vultures are done.

Marabous will also forage by wading in shallow water using their sensitive bills. When prey touches the bill it snaps shut and the bird swallows its catch. Increasingly, marabous have become dependent on human garbage and hundreds of these huge birds are seen around African dumps or waiting for a handout in urban areas. Marabous eating human garbage have been seen to devour virtually anything that they can swallow, including even shoes and pieces of metal.

27-12-2015 SAIGON, VIETNAM - EURASIAN TREE SPARROW (MALE) (Passer montanus)

The Eurasian tree sparrow (Passer montanus) is asmall passerine bird that breeds over most of temperate Eurasia and Southeast Asia, where it is known as the Tree sparrow. It has been introduced elsewhere including the United States, where it is known as the Eurasian tree sparrow or German sparrow to differentiate it from the native unrelated American tree sparrow.

The adult's crown and nape are rich chestnut, and there is a kidney-shaped black ear patch on each pure white cheek; the chin, throat, and the area between the bill and throat are black. The upperparts are light brown, streaked with black, and the brown wings have two distinct narrow white bars. The legs are pale brown, and the bill is lead-blue in summer, becoming almost black in winter. This sparrow is distinctive even within its genus in that it has no plumage differences between the sexes; the juvenile also resembles the adult, although the colors tend to be duller. Its contrasting face pattern makes this species easily identifiable in all plumages; the smaller size and brown, not grey, crown are additional differences from the male house sparrow. Adult and juvenile Eurasian tree sparrows undergo a slow complete molt in the autumn and show an increase in body mass despite a reduction in stored fat. The change in mass is due to an increase in blood volume to support active feather growth and generally higher water content in the body.

19-12-2015 MALACCA, MALAYA - MALAYAN NIGHT HERON (Gorsachius melanolophus)

The Malayan night heron (Gorsachius melanolophus), also known as Malaysian night heron and tiger bittern, is a medium-sized heron. It is distributed in southern and eastern Asia.

The Malayan night heron has been found in India, Sri Lanka, Brunei, Nepal, Bangladesh, Myanmar, Cambodia, Laos, Vietnam, Thailand, Malaysia, Singapore, China, Indonesia, the Philippines, Taiwan and Japan. It is a vagrant in Palau and Korea. Its range size is estimated at 1,240,000 km2. One roadkilled bird was discovered on Christmas Island, Australia where it is likely a vagrant. This bird occurs in forests, streams, and marshes. In Japan, population densities of the herons increased as undisturbed forest cover on islands increased.

The Malayan night heron is about 48 cm (19 in) long. The wingspan is about 86 cm (34 in). It is stocky, with a short beak. Its neck and breast are rufous. There are streaks going down the centre of the neck to the breast. The upperparts are chestnut and vermiculated. The flight feathers are blackish. The crown is black, the chin is white, and the eyes are yellow. The beak is black and the legs are greenish. The juvenile is greyish to rufous and is spotted and vermiculated. Males have been reported to have deeper blue lores and a longer crest compared to females during the breeding season. Males develop the dark blue lores 30-60 days prior to pair-bonding, while females had bluish-green lores when they first appeared in the breeding areas. Colours of the lores of both sexes faded as incubation progressed, with colours changing to bluish-green to green to greyish-green. If pairs laid a second clutch, the colouration of their lores were duller than the colouration during the first clutch.

The Malayan night heron is usually solitary. It roosts in trees and feeds in open areas. It seems to nest singly and not colonially in association with other waterbirds. In Taiwan, nests are sometimes close to urban buildings and feed on earthworms and frogs in open areas amid buildings. Birds with immature plumage attempt to disrupt pair bonding of adults, and sometimes immature birds are seen bonded with adults though their ability to build nests seemed poor. In one observed instance, people assisted an immature-adult pair by building a base for a poorly constructed nest. Of six breeding pairs observed in Taiwan, four were immature-adult pairs suggesting that the species in Taiwan has few breeding adults. Birds in immature plumage appeared to be sexually mature

Its territorial call is deep oo notes. It also produces hoarse croaks and arh, arh, arh.

The most common food items are earthworms and frogs, and it will sometimes eat fish. A study of its pellets found reptiles, snails, chilopods, arachnids, crabs and insects. Pellets of breeding birds in Korea had earthworms, snails and cicadas. An instance of predation of the Brown Anole Anolis sagrei has been observed.

The bird has a large range and its global population is between 2,000 and 20,000 individuals. Its population trend is not known, but it does not meet the criteria for a vulnerable species status.

20-12-2015 JURONG, SINGAPORE - BLUE CROWNED HANGING PARROT (Loriculus galgulus)

The blue-crowned hanging parrot (Loriculus galgulus) is a parrot species endemic to southern Burma and Thailand, Malaya, Singapore, and Indonesia (Sumatra, Java, Borneo). These parrots are 12cm in height and weight 28g and have a longevity of 14 years. They are recognized by their green plumage, black beak and characteristic blue feathers arranged like a crown on their head.

Blue-crowned hanging parrots have green plumage and adults have black beaks. There is sexual dimorphism between males and females of the species. Adult males have a characteristic blue "crown" patch on their head and a red mark on their throat as well as a red rump bordered by a yellow lower back. Adult females plumage is duller green in color compared to the males, they do not have the red throat mark and have a less apparent or absent blue crown on the head and lack yellow feathers on their lower back. Juveniles' plumage is dull green, they also have little to no blue crown patch, they have a little to no blue crown visible and their bills are light in color.

The calls these birds make when flying are shrill and squeaky. When flying in flocks, the calls can be described as rapid and ringing. As they forage, they utter shrill two-syllable calls.

20-12-2015 JURONG, SINGAPORE - AUSTRALIAN PELICAN (Pelecanus conspicillatus)

6-1-2016 HONG KONG AVIARY - WHITE NAPED YUHINA (Yuhina bakeri)

The white-naped yuhina (Yuhina bakeri ) is a bird species in the white-eye family Zosteropidae.

It is found from the Himalayas to northern Myanmar. Its natural habitats are temperate forests and subtropical or tropical moist lowland forests.

Exquisite yuhina with an orange head and crest with white ears and throat. Nape is not obviously pale, but the white “trim” to the back edge of the crest is noticeable. Forages in broadleaf forests from lower foothills up to montane areas. Social and often seen in large flocks, occasionally with other species. Vocal; gives a range of calls, including fluid-sounding twitters and a nasal bleating.

27-12-2015 SAIGON, VIETNAM - CHINESE POND HERON (Ardeola bacchus)

The Chinese pond heron (Ardeola bacchus ) is an East Asian freshwater bird of the heron family, (Ardeidae).

It is one of six species of birds known as "pond herons" (genus Ardeola ). It is parapatric (or nearly so) with the Indian pond heron (A. grayii ) to the west and the Javan pond heron (A. speciosa ) to the south, and these three are presumed to form a superspecies. As a group they are variously affiliated with the squacco heron (A. ralloides ) or the Malagasy pond heron (A. idae ). As of mid-2011 there are no published molecular analyses of pond heron interrelationships and osteological data is likewise not analyzed for all relevant comparison taxa.

The Chinese pond heron is typically 47 cm (19 in) long with white wings, a yellow bill with a black tip, yellow eyes and legs. Its overall colour is red, blue and white during breeding season, and greyish-brown and flecked with white at other times.

It is found in shallow fresh and salt water wetlands and ponds in China and adjacent temperate and subtropical East Asia. Essentially a lowland bird, its range is delimited by the subarctic regions in the north, and by the mountain ranges in the west and south.

The species is prone to some vagrancy. One individual in breeding plumage was seen by the river at Bonzon near Gangaw – just inside the Chin State of Burma – west of the species' usual range, on April 8, 1995. A stray bird stopping over on Saint Paul Island, Alaska on August 4–9, 1997 was the first recorded occurrence of this species in North America.

Its food consists of insects, fish, and crustaceans. The Chinese pond heron often nests in mixed-species heronries. It lays a clutch of 3–6 blue-green eggs.

19-12-2015 MALACCA, MALAYA - EURASIAN TREE SPARROW (MALE) (Passer montanus)

The Eurasian tree sparrow (Passer montanus) is asmall passerine bird that breeds over most of temperate Eurasia and Southeast Asia, where it is known as the Tree sparrow. It has been introduced elsewhere including the United States, where it is known as the Eurasian tree sparrow or German sparrow to differentiate it from the native unrelated American tree sparrow.

The adult's crown and nape are rich chestnut, and there is a kidney-shaped black ear patch on each pure white cheek; the chin, throat, and the area between the bill and throat are black. The upperparts are light brown, streaked with black, and the brown wings have two distinct narrow white bars. The legs are pale brown, and the bill is lead-blue in summer, becoming almost black in winter. This sparrow is distinctive even within its genus in that it has no plumage differences between the sexes; the juvenile also resembles the adult, although the colors tend to be duller. Its contrasting face pattern makes this species easily identifiable in all plumages; the smaller size and brown, not grey, crown are additional differences from the male house sparrow. Adult and juvenile Eurasian tree sparrows undergo a slow complete molt in the autumn and show an increase in body mass despite a reduction in stored fat. The change in mass is due to an increase in blood volume to support active feather growth and generally higher water content in the body.

18-12-2015 LOMUT, MALAYSIA - CRAB EATING MACAQUE MONKEY (Macaca fascicularis)

The crab-eating macaque (Macaca fascicularis), also known as the long-tailed macaque and referred to as the cynomolgus monkey in laboratories, is a cercopithecine primate native to Southeast Asia. A species of macaque, the crab-eating macaque has a long history alongside humans. The species has been variously seen as an agricultural pest, a sacred animal, and, more recently, the subject of medical experiments.

The crab-eating macaque lives in matrilineal social groups of up to eight individuals dominated by females.they reach puberty. It is an opportunistic omnivore and has been documented using tools to obtain food in Thailand and Myanmar. The crab-eating macaque is a known invasive species and a threat to biodiversity in several locations, including Hong Kong and western New Guinea. The significant overlap in macaque and human living space has resulted in greater habitat loss, synanthropic living, and inter- and intraspecies conflicts over resources.

Macaca comes from the Portuguese word macaco, which was derived from makaku, a word in Ibinda, a language of Central Africa (kaku means monkey in Ibinda). The specific epithet fascicularis is Latin for a small band or stripe. Sir Thomas Raffles, who gave the animal its scientific name in 1821, did not specify what he meant by the use of this word.

In Indonesia and Malaysia, the crab-eating macaque and other macaque species are known generically as kera, possibly because of their high-pitched cries.

The crab-eating macaque has several common names. It is often referred to as the long-tailed macaque due to its tail, which is often longer than its body. The name crab-eating macaque refers to its being often seen foraging beaches for crabs. Another common name for M. fascicularis is the cynomolgus monkey, from the name of a race of humans with long hair and handsome beards who used dogs for hunting according to Aristophanes of Byzantium, who seemingly derived the etymology of the word cynomolgus from the Greek κύων, cyon 'dog' (gen. cyno-s) and the verb ἀμέλγειν, amelgein 'to milk' (adj. amolg-os), by claiming that they milked female dogs. This name is commonly used in laboratory settings.

The body length of the adult, which varies among subspecies, is 38–55 cm (15–22 in) with relatively short arms and legs. Males are considerably larger than females, weighing 5–9 kg (11–20 lb) compared to the 3–6 kg (6.6–13.2 lb) of females. The tail is longer than the body, typically 40–65 cm (16–26 in), which is used for balance when they jump distances up to 5 m (16 ft). The upper parts of the body are dark brown with light golden brown tips. The under parts are light grey with a dark grey/brown tail. Crab-eating macaques have backwards-directed crown hairs which sometimes form short crests on the midline. Their skin is black on their feet and ears, whereas the skin on the muzzle is a light grayish pink color. The eyelids often have prominent white markings and sometimes there are white spots on the ears. Males have a characteristic mustache and cheek whiskers, while females have only cheek whiskers. Crab-eating macaques have a cheek pouch which they use to store food while foraging. Females show no perineal swelling.

The crab-eating macaque's native range encompasses most of mainland Southeast Asia, from extreme southeastern Bangladesh south through the Malay Peninsula and Singapore, the Maritime Southeast Asia islands of Sumatra, Java, and Borneo, offshore islands, the islands of the Philippines, and the Nicobar Islands in the Bay of Bengal. This primate is a rare example of a terrestrial mammal that violates the Wallace line, being found out across the Lesser Sunda Islands. It lives in a wide variety of habitats, including primary lowland rainforests, disturbed and secondary rainforests, shrubland, and riverine and coastal forests of nipa palm and mangrove. It also easily adjusts to human settlements and is considered sacred at some Hindu temples and on some small islands, but as a pest around farms and villages. Typically, it prefers disturbed habitats and forest periphery.

The crab-eating macaque is an introduced alien species in several countries, including Hong Kong, Taiwan, West Papua, Papua New Guinea, New Britain, New Ireland, New Caledonia, Solomon Islands, Fiji, Tonga, Samoa, Nauru, Vanuatu, Pohnpei, Anggaur Island in Palau, and Mauritius. This has led the Invasive Species Specialist Group of the International Union for Conservation of Nature to list the crab-eating macaque as one of the "100 of the World's Worst Invasive Alien Species". In Mauritius, it is a threat for the endemic and endangered Roussea simplex, as it destroys its flowers. It also hinders germination of some endemic trees by destroying most of their fruits when unripe and competes with the endemic endangered Mauritian flying fox for native fruits.

Where it is not a native species, particularly on island ecosystems whose species often evolved in isolation from large predators, it is a documented threat to many native species. The immunovaccine porcine zona pellucida (PZP), which causes infertility in females, is currently being tested in Hong Kong to investigate its use as potential population control.

Macaques live in social groups that contain three to 20 females, their offspring, and one or many males. The groups usually have fewer males than females. In social groups of macaques, a clear dominance hierarchy is seen among females. These ranks remain stable throughout the female's lifetime and also can be sustained through generations of matrilines. Females have their highest birth rates around 10 years of age and completely stop bearing young by age 24.

The social groups of macaques are female-bonded, meaning the males will disperse at the time of puberty. Thus, group relatedness on average appears to be lower than compared to matrilines. More difference in relatedness occurs when comparing high-ranking lineages to lower ranking lineages, with higher-ranking individuals being more closely related to one another. Additionally, groups of dispersing males born into the same social groups display a range of relatedness, at times appearing to be brothers, while at other times appearing to be unrelated.

In addition to the matrilineal dominance hierarchy, male dominance rankings also exist. Alpha males have a higher frequency of mating compared to their lower-ranking conspecifics. The increased success is due partially to his increased access to females and also due to female preference of an alpha male during periods of maximum fertility. Though females have a preference for alpha males, they do display promiscuous behavior. Through this behavior, females risk helping to rear a non-alpha offspring, yet benefit in two specific ways, both in regard to aggressive behavior. First, a decreased value is placed on one single copulation. Moreover, the risk of infanticide is decreased due to the uncertainty of paternity.

Increasing group size leads to increased competition and energy spent trying to forage for resources, and in particular, food. Further, social tensions build and the prevalence of tension-reducing interactions like social grooming fall with larger groups. Thus, group living appears to be maintained solely due to the safety against predation.

Crab-eating macaques sometimes form mixed species groups with other primate species, including the southern pig-tailed macaque, dusky langur and white-thighed surili. They have been observed engaging in grooming with other primate species, including the southern pig-tailed macaque and leaf monkeys such as Raffles' banded langur and the dusty langur.

Group living in all species is dependent on the tolerance of other group members. In crab-eating macaques, successful social group living requires postconflict resolution. Usually, less dominant individuals lose to a higher-ranking individual when conflict arises. After the conflict has taken place, lower-ranking individuals tend to fear the winner of the conflict to a greater degree. In one study, this was seen in the ability to drink water together. Postconflict observations showed a staggered time between when the dominant individual begins to drink and the subordinate. Long-term studies reveal the gap in drinking time closes as the conflict moves further into the past.

Grooming and support in conflict among primates is considered to be an act of reciprocal altruism. In crab-eating macaques, an experiment was performed in which individuals were given the opportunity to groom one another under three conditions: after being groomed by the other, after grooming the other, and without prior grooming. After grooming took place, the individual that received the grooming was much more likely to support their groomer than one that had not previously groomed that individual. These results support the reciprocal altruism theory of grooming in long-tailed macaques.

Crab-eating macaques demonstrate two of the three forms of suggested postconflict behavior. In both captive and wild studies, the monkeys demonstrated reconciliation, or an affiliative interaction between former opponents, and redirection, or acting aggressively towards a third individual. Consolation was not seen in any study performed.

Postconflict anxiety has been reported in crab-eating macaques that have acted as the aggressor. After a conflict within a group, the aggressor appears to scratch itself at a higher rate than before the conflict. Though the scratching behavior cannot definitely be termed as an anxious behavior, evidence suggests this is the case. An aggressor's scratching decreases significantly after reconciliation. This suggests reconciliation rather than a property of the conflict is the cause of the reduction in scratching behavior. Though these results seem counterintuitive, the anxiety of the aggressor appears to have a basis in the risks of ruining cooperative relationships with the opponent.