Nankeen Night Heron

Identificazione

The nankeen night heron is a medium-sized heron. The adult male is 55 to 65 cm in length, while the female is slightly smaller, measuring 55 to 60 cm. Its weight varies from 810 g to 1014 g, and the wingspan ranges from 95 to 105 cm. Other than females being smaller in most measurements, the sexes of the nankeen night heron are alike in appearance.<p>The nankeen night heron has a heavy black bill, which is similar in length as its head. The face is white with a cinnamon tint, and the nape and crown of breeding adults is a grey-black. During the breeding season, there are also usually two or three thin, white plumes from the crown in a downward direction to the neck. These are tipped with black when newly grown. The heron has a rich chestnut colour across the upperparts, and the colours are more intense in the breeding season. The underparts of the nankeen night heron are white, and there is a gradual blend of the chestnut colour and the white on its neck and upper breast. The back, tail, and upper wing of the bird are a rich rufous colour. The iris is of a straw yellow and can be tinged with orange during the breeding season, while the legs and feet are a creamy yellow. Their legs are relatively shorter than that of other herons, and can become bright pink during courtship and early breeding.<p>Juvenile nankeen night herons are quite different in appearance compared to adults, with the top of their head and their nape being a black-brown colour and streaked with beige. The upper throat and chin are white, while the rest of the neck is heavily streaked with brown. The tail of juveniles is rufous-brown, the legs and feet are lime-green to olive-grey, and the bill is a dull olive-yellow colour with black on the tip. Nankeen night heron chicks are covered with dark brown down feather on their back and white on the undersides. They have cream coloured beaks with a dark grey edge, and the legs are olive.<p>Adult male nankeen night herons give a qu-arck sound when departing their roost at night, while females and juvenile nankeen night herons give a higher pitched qu-ook sound. When disturbed during roosting, the heron gives a short, deep quock. The nankeen night heron gives a hoarse, croaking quok when in flight, and a harsh croak sound while feeding in a group. The threat call of the bird is a rok sound and is used when in aggregations. Nankeen night heron chicks are described to beg with a kak-kakkak call in their first two weeks, in order to obtain the attention of their parents for feeding. They also squawk as they dispute among themselves. After leaving their nest, during the period when they are still flightless, young nankeen night herons utter a noisy high-pitched screech when alarmed.

Tassonomia

The nankeen night heron was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with herons, cranes and storks in the genus Ardea and coined the binomial name Ardea caledonica. Gmelin based his description on the "Caledonian night heron" that had been described in 1875 by the English ornithologist John Latham in his multi-volume work A General Synopsis of Birds. The heron had been observed in September 1774 on the island of New Caledonia during Captain James Cook's second voyage to the Pacific Ocean. The naturalist Johann Reinhold Forster, who had accompanied Cook on the voyage, provided Latham with a description of the species. The nankeen night heron is now placed in the genus Nycticorax that was introduced in 1817 by the English naturalist Thomas Forster to accommodate the black-crowned night heron. The epithet nycticorax is from Ancient Greek and combines nux, nuktos meaning "night" and korax meaning "raven". The word was used by authors such as Aristotle and Hesychius of Miletus for a "bird of ill omen", perhaps an owl. The word was used by the Swiss naturalist Conrad Gessner in 1555 and then by subsequent authors for the black-crowned night heron. The term nankeen in the common name of the species is defined as 'a type of pale-yellow cotton cloth, originally from China' in the Cambridge Dictionary. The term originates from the city of Nanjing, which is where the material was first made. In the alternative name of the species, rufous night heron, the word rufous refers to a reddish-brown colour and more accurately describes the colour of the bird's plumage. This name is widely used in regions such as New Guinea and Wallacea.<p>Six subspecies are recognised:

Nome scientifico

Nycticorax caledonicus

Autorità

(Gmelin, JF, 1789)

Ordine

Pelecaniformi

Famiglia

Ardeidae

Genere

Nycticorax

Areale e habitat

Nankeen night herons have a broad distribution and are found in Australia, New Zealand, the Philippines, Papua New Guinea, the Solomon Islands, Java, New Caledonia, Palau, and the Caroline Islands, Federated States of Micronesia. They are native to Australia and are widespread in most states of the country except for the west, in which it is rare or absent. Nankeen night herons have six subspecies, which includes the Bonin nankeen night heron (Nycticorax caledonicus crassirostris). This subspecies was endemic to Bonin Islands, Japan, but has been extinct since the late 1800s.<p>The nankeen night heron is resident in a wide range of habitats, which includes grasslands, meadows, forests, lagoons, beaches, reefs, marshes, shores, wetlands, and swamps. It is most commonly found near rivers and streams. The species prefer habitats with emergent vegetation when near permanent water. The nankeen night heron is mainly nocturnal, and thus roosts during the daytime in dense cover of trees, bushes, and reeds. In more exposed situations, they are also known to roost in dead trees. In urban areas, the nankeen night heron favours nesting and roosting in trees such as cypresses and pines. They also reside in urban wetlands, dry fields, gardens, ponds, airports, and parks.

Migrazione

Migratori completi

Comportamento

Comportamento migratorio: Migratori completi.

Conservazione

Tendenza della popolazione: stabile.

Tendenza della popolazione

stabile