L'Aigrette à face blanche, appelée également Aigrette australienne (Egretta novaehollandiae), est une espèce d'échassier appartenant à la famille des Ardeidae commun dans la majeure partie de l'Australasie copmme en Nouvelle-Guinée, dans les îles du détroit de Torres, en Indonésie, en Nouvelle-Zélande, dans les îles subantarctiques et dans toute l'Australie en dehors des régions les plus sèches. C'est un petit héron, au plumage clair, légèrement gris-bleu, aux pattes jaunes et portant des marques blanches sur la face. On la trouve près des eaux peu profondes, douces ou salées, et bien qu'elle s'éloigne avec de longs et lents battements d'ailes si elle est dérangée, elle n'hésite pas à mener des raids audacieux dans les étangs de pisciculture en bordure de ville.

Taxonomie
L'espèce a été initialement décrite par l'ornithologue John Latham en 1790. Elle a été considérée à une certaine époque comme étroitement liée au genre Ardea, puis a été placée pendant un certain temps dans son propre genre en raison de l'absence de plumes typiques du genre. Son apparence et son comportement sont plus étroitement liés à ceux du genre Egretta comme confirmé par l'analyse de l'ADN. On avait décrit des sous espèces E. n. novaehollandiae et E. n. parryi en Australie, E. n. nana en Nouvelle-Calédonie et E. n. austera dans la province indonésienne de Papouasie mais elles ne sont plus reconnues.

Description
L'Aigrette australienne a un plumage d'un bleu-gris clair. Le front, la couronne, le menton et la partie supérieure de la gorge sont blancs. La tache de la couronne est de forme variable, avec le blanc descendant de temps en temps jusqu'au cou, cette variabilité rendant possible l'identification des individus. L'iris est gris, vert, jaune terne ou cannelle. Les lores sont noirs. Le bec est noir et souvent gris pâle à la base. Au cours de la saison de reproduction des plumes rose-brun ou bronze apparaissent sur la gorge et la poitrine, avec des plumes bleu-gris sur le dos. L'adulte pèse généralement 550 g et mesure 60 à 70 cm de hauteur. Les jeunes oiseaux sont gris pâle avec la gorge blanche et ont souvent une couleur rougeâtre sur le dessous. Les poussins sont généralement gris sur le bas.

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The White-faced Heron, Egretta novaehollandiae, also known as the White-fronted Heron, and incorrectly as the Grey Heron, or Blue Crane, is a common bird throughout most of Australasia, including New Guinea, the islands of Torres Strait, Indonesia, New Zealand, the islands of the Subantarctic, and all but the driest areas of Australia. It is a relatively small heron, pale, slightly bluish-grey, with yellow legs and white facial markings. It can be found almost anywhere near shallow water, fresh or salt, and although it is prompt to depart the scene on long, slow-beating wings if disturbed, it will boldly raid suburban fish ponds.

Taxonomy
The species was originally described by ornithologist John Latham in 1790. It was historically considered to be closely related to Ardea but for some time it was placed in its own genus because of the absence of the plumes typical in that genus. Appearance and behaviour are more closely related to those in the genus Egretta, which DNA analysis has confirmed. Subspecies E. n. novaehollandiae and E. n. parryi in Australia, E. n. nana from New Caledonia and E. n. austera from Irian Jaya have previously been described, but are now not recognised taxonomically.

Description
The adult White-faced Heron is relatively small, pale blue-grey. The forehead, crown, chin and upper throat are white. The crown pattern is variable, with the white occasionally spreading down the neck; the variability makes identification of individuals possible. The iris may be grey, green, dull yellow or cinnamon. The regions between the eye and bill on the side of the head (lores) are black. The beak is black and often pale grey at the base. During the breeding season pinkish-brown or bronze nuptial plumes appear on the foreneck and breast, with blue-grey plumes appearing on the back. The adult typically weighs 550 g and ranges from 60–70 cm in height. Immature birds are paler grey with only the throat white, and often have a reddish colour on the underparts. Chicks are typically covered with grey down.

Distribution and habitat
The White-faced Heron is found throughout most of Australasia, including New Guinea, the islands of Torres Strait, Indonesia, New Caledonia, New Zealand, the islands of the sub-Antarctic, and all but the driest areas of Australia. The species is now resident on Christmas Island but has not yet been recorded breeding there. It is also commonly found on Lombok, Flores and Sumbawa, and has appeared as a vagrant in China,[7] the Cocos Islands and the Solomon Islands. It is mostly a winter visitor to the Northern Territory It was self-introduced to New Zealand in the late 1940s. It is the only heron recorded breeding in Tasmania. The White-faced Heron is locally nomadic and found in both fresh and salty wetlands, farm dams, pastures, grasslands, crops, shores, saltmarsh, tidal mudflats, boat-harbours, beaches, golf courses, orchards or in garden fish-ponds. It is protected in Australia under the National Parks and Wildlife Act, 1974.

Behaviour
The White-faced Heron typically perches on fence-posts, trees, telephone poles and house roofs. Its flight is slow and bouncing.

Call
The most common call of the White-faced Heron is a gravelly croak or gobble, graak or graaw and is typically given in flight, in interactions or in aggressive encounters. Another call, gow, gow, gow is typically given upon returning to a nest. High pitched wrank, oooooooooh or aaarrrgh calls are given as alarm calls.

Breeding
Breeding generally takes place in the spring, but the birds may breed at other times in response to rainfall. Breeding generally takes place in southern Australia, and birds disperse for long distances at other times of year. Both sexes share the task of building the nest, incubating the eggs and caring for the young. The nest is an untidy shallow bowl, made of sticks and usually placed on a leafy branch 5–12 m high, at altitudes from sea level to over 1000 m. When breeding the birds have long feathers (nuptial plumes) on the neck, head and back. A typical clutch has 3-5 pale blue eggs. with an average size of 48.5×35 mm. Normally only one brood is raised per year. Incubation lasts approximately 25 days. The parents guard the chicks for 3–4 weeks and fledging takes place 40 days after hatching. Typical nestling predators include kookaburras, Australian Magpies, harriers and owls.

Feeding
White-faced Herons eat most small aquatic creatures and their varied diet is fish, frogs, small reptiles and insects. It uses a variety of techniques to find food including standing still and waiting for prey movement (often employing a peculiarly rhythmic neck movement whether in water or on land), walking slowly in shallow water, wing flicking, foot raking or even chasing prey with open wings. White-faced Herons generally feed solitarily or independently in small groups. White-faced Herons are generally territorial during breeding season but may feed in groups during non-breeding season, particularly after rain or flooding.