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Black-crowned
Night Heron

Nycticorax nycticorax

Pucung Kuak (Malay)

perched on a branch showing white nape plume Black-crowned Night Herons are small stocky, short-legged compared to other herons. They are handsomely attired in a tri-colour plumage of black, grey and white, with two long plumes on the nape.

Night Herons are unpopular with other herons, which attack the Night Herons on sight. This is because Night Herons are very aggressive and steal eggs and young of other heron colonies. Perhaps it is the harassment from other birds that force Night Herons to come out mainly at night.

Besides fish, Black Crowned Night Herons eat a wide range of prey from aquatic invertebrates (crustacea, mussels, squid), amphibians and reptiles (lizards, snakes) to land invertebrates (leeches, earthworms, insects) including small mammals (rodents). They also eat plants and are not above eating carrion and rooting around garbage dumps.

Prey is shaken vigorously until stunned or killed and then juggled about in the beak and swallowed head first. They have strong digestive acids that can dissolve even bones. Their faeces are white and limey because of the dissolved calcium.

Mangrove and wetland wildlife at
Sungei Buloh Nature Park
Main features: Small (58-65cm, 0.7-1kg): black crown and back; grey wings and tai; white underparts; eyebrows and lores whitish; bill black slightly curved downward; legs and toes yellow (pinkish-red in breeding); eyes red. Genders look alike.

Juvenile: Very different in appearance: dark brown overall with wings white spotted; head white streaks; underparts white spotted or streaked.
non-breeding adult showing white nape plume
Non-breeding adult
juvenile showing white streaked plumage
Juvenile
Call: Harsh kwark or kwok, in flight or at roost. But there are many different interpretations of their calls.

In flight: Tucks its neck close to its body and its short legs barely extends beyond its tail; white underparts obvious.

Similar birds: Juveniles look like the juveniles of the Little Heron (Butorides striatus), Cinnamon Bittern (Ixobrychus cinnamomeus); these all lack the Black-crowned's spots on the back, stocky shape and robust bill.

Status in Singapore: Common resident throughout the island including North and South offshore islands (Pulau Ubin and Pulau Tekong).

World distribution: Nearly world-wide, except Australia and Antarctica. Resident on the Asian subcontinent, visitors to the Philippines and Borneo.

Classification: Family Ardeidae. World 65 species, Singapore 17 species.
at the water's edge with neck outstretched
They have surprisingly long necks
Like other herons, Night Herons hunt in shallow waters using their long necks and thick bills to snatch at prey.

Slow patient stalkers, they may remain motionless for long periods, standing with their neck tucked in, giving their typical hunched posture.

Black Crowned Night Herons may also hunt by vibrating their bills in the water to lure prey into investigating the disturbance. They may walk about or even swim when searching for food.
two birds in a confrontation
A breeding bird with red legs
intimidates a non-breeding one
Although they roost and nest together, and may even travel to feeding sites in a flock, they usually hunt alone and fiercely defend a feeding territory from others of their kind.

Although they may fly around during the day, Night Herons hunt throughout the night and early morning when the other herons are sleeping. But when food is scarce or in high demand (e.g., during the breeding season), they may also hunt during the day.
Juveniles and adults out of breeding season may also hunt during the day, possibly because other herons consider them less of a threat.

Black Crowned Night Herons prefer to nest and roost in mangroves, but prefer to hunt in freshwater wetlands. They travel to and from these hunting sites in long skeins in the evening, returning at dawn. They are found wherever there are suitable trees for roosting and nesting. Usually near brackish and freshwater wetlands: mangroves, mudflats, estuaries, ponds, reservoirs, canals, rivers. But they have also been observed in suburbs of large cities.

Breeding: Black Crowned Night Herons appear to breed year-round. In Singapore, they used to nest in Khatib Bongsu before fogging chased them off. One colony of about 20 pairs survive at the Jurong Lake area. Elsewhere, they have been known to roost in huge breeding colonies containing tens of thousands of birds.

During breeding season, their head plumes become longer, their black plumage take on a bluish-green gloss and their legs, feet and lores turn red. Believed to be monogamous, the males perform an elaborate courtship ritual, usually at night. They clapper their bills as they walk in a crouch, followed by wing flapping and a song and a dance (hissing as they rock from foot to foot). At first, the female may be rejected, but eventually she is accepted and they preen each other. During courtship, the male also presents sticks to his chosen female. When the pair bond is formed, their legs blush a pinkish-red!

Black Crowned Night Herons nest in colonies, sometimes with other colonies of herons. In the Malay-Thai peninsula, they prefer to nest in mangroves, especially in the Avicennia spp. Elsewhere, they may nest in coconut palms, bushes, reeds as well as at ground level on grassy tussocks. The nest is a made of sticks, twigs and reeds, lined with softer materials like roots and grass. The first nest built by young birds are fragile, but as they re-use the nest over the years, it become a bulky platform. Large colonies in mangrove trees, however, can kill the nest trees by heavy coatings of their dropping, forcing them to relocate regularly. The male usually begins the nest building by repairing an old one or starting a new one. Eventually, the pair divide the work between them, the male gathering the sticks and the female doing most of the constructing.

3-6, average 3, pale blue-green eggs are laid. Both parents incubate. On hot days, they may cool off the eggs by wetting their feathers. In 24-26 days, nearly naked hatchlings emerge. Both parents raise the young on regurgitated food at first, then whole prey as they young are older. The young usually scramble out of the nest and wait nearby for their parents to return. They are aggressive and will throw up on intruders. As a last resort, they may throw themselves into the water and paddle away. When parents return to the nest, they signal to the young so they know they are not predators, by bowing to show their glossy black crown and long white head plumes.
You can estimate the age of a young bird by its coloration.

juvenile showing white-streaked plumageBefore they are a year old, they look very different from the adults; dark brown with white streaks and spots.

juvenile
When they are 2 years old, the crown and back are brownish-black; rest of body brown; underparts with faint streaking. They get their adult colouring at age 3 years when they reach breeding age.

adult with red eyesOnly adults have bright red eyes, juveniles first have grey eyes which turn yellow then red.
The young fledge in about 2-3 weeks but don't leave their parents until about 6-7 weeks. They can live for about 20 years in the wild and 30 years in captivity.

Migration: Most Black Crowned Night Heron populations in our region are resident. A few populations that breed in the north may migrate, doing so at night and resting during the day. During their migration, they call to keep together.

Status and threats: Although Black Crowned Night Herons are among the most common herons in the world, this bird is on the Red Data list of Singapore. It is threatened by habitat loss; its preferred habitat are considered mosquito breeding sites and are not tolerated near human homes or regularly fogged. One traditional breeding site in Singapore was at Khatib Bongsu where up to 1,200 birds nested. This colony was destroyed by fogging which poisoned the birds. The birds have not returned. The birds' popularity is not aided by the fact that they are also a carrier of Japanese Encephalitis, a dangerous disease. In other parts of the world, they have been hunted for food (they apparently taste good, especially the young birds) or as a pest at fish farms. Like other wetland inhabitants, they are also threatened by water pollution and the overuse of pesticides.


LINKS REFERENCES
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Nature's Niche
  • Morten Strange, "A Photographic Guide to Birds of Malaysia and Singapore: including Southeast Asia, the Philippines and Borneo", Periplus, 2000 (p. 53: description, voice, habits, distribution, status, photo).
  • David R Wells, "The Birds of the Thai-Malay Peninsula: Vol. 1 (Non-Passarines)", Academic Press, 1999 (p. 91-93: identification, distribution map, habits, habitat, migration, conservation).
  • Lim Kim Seng, "Pocket Checklist of the Birds of the Republic of Singapore", Nature Society (Singapore), 1999 (Abundance, status, Chinese and Malay names).
  • Lim Kim Seng and Dana Gardner, "Birds: An Illustrated Field Guide to the Birds of Singapore", Sun Tree Publishing Ltd., 1997 (p. 85: identification, status in Singapore, distribution, diagram, number of species)
  • G W H Davison and Chew Yen Fook, "A Photographic Guide to Birds of Peninsular Malaysia and Singapore", New Holland Publishers Ltd., 1995 (p. 19: identification, status in Singapore, distribution, photo).
  • Morten Strange and Allen Jeyarajasingam, "Birds: A Photographic Guide to the Birds of Peninsular Malaysia and Singapore", Sun Tree Publishing, 1993 (p.112: description, distribution, habits, habitat, photo).
  • Clive Briffett, "A Guide to the Common Birds of Singapore", BP Science Centre,1992 (p. 47: habit, habitat, breeding site in Singapore)
  • P K L Ng and Y C Wee (ed.), "The Singapore Red Data Book", The Nature Society, 1994 (p.230: habits, habitat, distribution and breeding site in Singapore).
  • Peter K L Ng (ed.), "A Guide to the Threatened Animals of Singapore", BP Science Centre, 1995 (p. 128: photo, habitat, threats)
  • Christopher Hails, "Birds of Singapore" illustrated by Frank Jarvis, Times Editions, 1987 reprinted 1995 (p. 56: habits, description, status in Singapore, and lovely drawings of the birds).
  • Lim Kim Seng, "Vanishing Birds of Singapore", Nature Society (Singapore), 1992 (p. 20-21: distribution and status in Singapore and details of the effect of fogging on the breeding site at Khatib Bongsu; fact sheet on all aspects).
  • James Hancock, "Herons and Egrets of the World: A photographic journey", Academic Press, 1999 (p. 168-170: identification, distribution, status, feeding, breeding, and photos of all life stages)
  • John Palmer (ed.), "Exploring the Secrets of Nature", Reader's Digest, 1994 (p. 55: parents identifying themselves to chicks).
 
By Ria Tan, 2001