Black crowned Night Heron (Nycticorax nycticorax)

Black-crowned Night Heron

Black-crowned Night-Heron (Nycticorax nycticorax)

[order] Ciconiiformes | [family] Ardeidae | [latin] Nycticorax nycticorax | [UK] Black-crowned Night-Heron | [FR] Bihoreau gris | [DE] Nachtreiher | [ES] Martinete Común | [IT] Nitticora comune | [NL] Kwak

Physical charateristics

Black-crowned Night Heron is a stocky bird with large head, thick and short neck, and short legs.
Adult has black crown and mantle. Wings, rump and tail are grey. Underparts are whitish. Legs and feet are yellow-green.
In breeding season, adult has two long white hind neck feathers. Bill is pointed and black. Lores are blue grey, becoming red in breeding season. Eyes are red. Legs and feet turn pink in the height of breeding season. Its black plumage takes on bluish-green gloss. Both sexes are similar, but female is slightly smaller than male. Juvenile has brown upperparts with conspicuous white spotting. Underparts are streaked buff and white. Bill is greenish-yellow. Eyes are yellowish to amber. Legs and feet are dull grey. Juvenile needs three years to reach adult plumage, loosing year after year the pale spots on upperparts, and underparts becoming less streaked. When they hatch, chicks are partially covered with white and grey down.

wingspan min.: 98 cm wingspan max.: 110 cm
size min.: 58 cm size max.: 65 cm
incubation min.: 21 days incubation max.: 22 days
fledging min.: 40 days fledging max.: 50 days
broods: 1   eggs min.: 2  
      eggs max.: 7  

Distribution

Black-crowned Night Heron is largely nocturnal, foraging from dusk to dawn. It stands motionless, waiting for prey to pass by, and it snatches them up with its bill. It also raids nests of other herons or species to steal the chicks.
Black-crowned Night Heron shakes vigorously the prey to kill it, and then it swallows it head first. Their strong digestive acids can dissolve bones.
It hunts in shallow water, as other herons, using their thick bills to capture prey. They may remain motionless for long periods, with neck tucked in, standing in the water or on a branch, searching for prey. It usually hunts alone, and defends strongly its feeding area. It may hunt during the day is food is scarce or in high demand in nesting season. It also uses “bill vibrating”, opening and closing the bill quickly into the water, creating disturbances to lure prey and to catch them.
Black-crowned Night Heron is probably monogamous. Male performs an elaborate courtship display often at night. Male walks around in a crouch position, head lowered, and clapping its bill. Then, it flaps its wings, singing and dancing. It hisses while is rocking from foot to foot. When female accepts, they preen each other and engage mutual billing. During display, male can offer sticks to its mate. When pair bond is formed, legs turn pinkish-red. During this period, male is aggressive.
Black-crowned Night Heron migrates at night, resting during the day. When they migrate, they call to keep together, and fly in large flocks.

Listen to the sound of Black-crowned Night-Heron



Copyright remark: Most sounds derived from xeno-canto

Habitat

Black-crowned Night Heron lives near lakes, marshes and rivers with dense fringe vegetation and cattails. They nest and roost in trees. When they feed or migrate, we can find them in more open areas such as rice fields and open lagoons, in salt, brackish or freshwater marshes.

Foraging habits

The black-crowned night heron is an opportunistic feeder. Its diet consists mainly of fish, though it is frequently rounded out by other items such as leeches, earthworms, aquatic and terrestrial insects. It also eats crayfish, mussels, squid, amphibians, lizards, snakes, rodents, birds, eggs, carrion, plant materials, and garbage and refuse at landfills. It is usually a solitary forager, and it strongly defends its feeding territory. The night heron prefers to feed in shallow waters, where it grasps its prey with its bill instead of stabbing it. A technique called ‘bill vibrating’–which is opening and closing the bill rapidly in water–creates a disturbance which may lure prey. Evening to early morning are the usual times it feeds, but when food is in high demand, such as during the breeding season, it will feed at any time of the day.


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Breeding habits

Black-crowned Night Heron usually nests in colonies of about 12 pairs. After courtship displays, pair builds the nest near the trunk of a tree, or in a fork of branches. Male starts nest building, as a new nest or arranging and old one. Nest is a platform made with sticks and reeds, and lined with roots and grass. Nest may be located between 5 and 10 metres above the ground.
Female lays 3 to 5 pale blue eggs, at two days intervals. Incubation lasts about 24 to 26 days, shared by both parents. When weather is too hot, parents wet their feathers, probably to keep the eggs cool.
Chicks are brooded by both adults, and fed by regurgitation. As they grow, parents bring whole prey. Young are very noisy when they beg for food.
They leave the nest at about 3 weeks, climbing about and around the nest. They fledge at about 6 or 7 weeks of age and depart to the feeding grounds. Young defend themselves regurgitating food onto intruders when disturbed. They reach their sexual maturity at 2 or 3 years old.
This species produces only one brood per season.

Conservation

This species has a large range, with an estimated global Extent of Occurrence of 10,000,000 km². It has a large global population estimated to be 430,000-3,600,000 individuals (Wetlands International 2002). Global population trends have not been quantified, but the species is not believed to approach the thresholds for the population decline criterion of the IUCN Red List (i.e. declining more than 30% in ten years or three generations). For these reasons, the species is evaluated as Least Concern. (source Birdlife.org)

Black-crowned Night-Heron status Least Concern

Migration

Extensive post-breeding dispersal in all directions, in Europe starting in June. North populations migratory. From August, West Palearctic birds cross Mediterranean and Sahara on broad front, reaching tropical Africa and possibly further South, e.g. bird ringed in Romania recovered in Mozambique. Part of population remains to winter in Mediterranean Basin. Birds return to breeding grounds March-May. Most North American breeders winter in South USA, Central America and Caribbean, returning in March-May. North East Asian populations winter from China to Philippines and Indonesia. Tropical birds perform seasonal dispersive movements. Overshooting by Northern populations common in spring, birds occurring much further North than usual. Vagrancy also frequent, with records from Alaska, Greenland, Iceland, Azores, Micronesia, Galapagos, Hawaii, etc. Migration mainly takes place at night, typically solitary or in small flocks.

Black-crowned Night-Heron range map

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