Eastern great egret

The eastern great egret (Ardea alba modesta), a white heron in the genus Ardea, is usually considered a subspecies of the great egret (A. alba). In New Zealand it is known as the white heron or by its Māori name kōtuku. The subspecies was first described by British ornithologist John Edward Gray in 1831.

Ardea alba modesta
Breeding plumage in New Zealand
Non-breeding plumage in Tasmania
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Pelecaniformes
Family: Ardeidae
Genus: Ardea
Species:
A. alba
Subspecies:
A. a. modesta
Trinomial name
Ardea alba modesta
J.E. Gray, 1831
Yellow: breeding, green: year-round, blue: nonbreeding
Synonyms

Ardea modesta

Taxonomy

This species was originally described as the "pure white heron of India", Ardea modesta, by Gray in 1831,[1] but was later generally considered a synonym of Ardea alba, by Ellman in 1861 through to the Peters checklist in 1979.[2][3] It was elevated to species status again by Sibley and Monroe in 1990,[4] and this was supported by a 2005 revision of the herons.[5] It is still sometimes considered a subspecies of the great egret Ardea alba.[6]

Description

Measuring 83–103 cm (33–41 in) in length and weighing 0.7–1.2 kg (1.5–2.6 lb), the eastern great egret is a large heron with all-white plumage. Its bill is black in the breeding season and yellow at other times,[7] and its long legs are red or black. The colours of the bare parts of the face change to green during the breeding season.[7] The breeding plumage is also marked by long neck plumes and a green facial area.[8] The eastern great egret can be distinguished from other white egrets and herons in Asia and Australia by its very long neck, one and a half times as long as its own body.[8]

Range and habitat

The eastern great egret has a wide distribution throughout Asia and Oceania, with breeding populations in Australia, Bangladesh, China, Nepal, India, Indochina, Indonesia, Japan, Korea, Myanmar, New Zealand, Pakistan, Papua New Guinea, Russia (north-eastern), Solomon Islands, Sri Lanka and Thailand. The egret breeds across Australia but only rarely in the southwest of the continent or dry interior.[9] The largest colonies within Australia are in the Top End and Channel Country, which can number several thousand pairs. Colonies in the southeast of Australia can number several hundred pairs.[8] The bird is an uncommon autumn and winter visitor to Tasmania.[10]

Behaviour

Feeding

The diet includes vertebrates such as fish, frogs, small reptiles, small birds and rodents, and invertebrates such as insects, crustaceans, and molluscs. The eastern great egret hunts by wading or standing still in shallow water and "spearing" prey with its bill.[8]

Breeding

The eastern great egret often breeds in colonies with other herons, egrets, cormorants, spoonbills and ibises. One brood is raised a year, although the breeding season varies within Australia. In the north of the country it is in March to May, in southern and central Queensland December and January, and October to December in the south. Located atop trees at a height of 20 m (60 ft) or more, the nest is a flat wide platform of dry branches and sticks with a shallow basin for eggs and young. The clutch consists of anywhere from two to six pale blue-green eggs, with three or four being the usual number. They are oval in shape and measure 52 x 36 mm.[9]

Status

The subspecies is protected in Australia under the National Parks and Wildlife Act 1974. In New Zealand the white heron is highly endangered, with only one breeding site at Okarito Lagoon.[7][11] It shares this site with the kōtuku ngutupapa, or Royal spoonbill. When H.M. Queen Elizabeth II visited New Zealand in 1953-54, she was compared to the kōtuku —a compliment to rare, distinguished visitors.[12] The egret is featured on the reverse side of a New Zealand $2 coin.

Images

References
  1. Gray, John Edward (1831). The Zoological Miscellany. London: Published by Treuttel, Wurtz and Co., G.B. Sowerby, W. Wood. doi:10.5962/bhl.title.113722.
  2. Ellman, J. B. (1861). The Zoologist : a monthly journal of natural history. 19. London. p. 7469.
  3. Ardea alba modesta J.E. Gray; Payne 1979, in Peters Check-list Birds World 1 (2nd edition): 204.
  4. Sibley, Charles G.; Monroe, Burt L. (1990). Distribution and taxonomy of birds of the world. New Haven: Yale University Press. ISBN 0-300-04969-2. OCLC 23248877.
  5. Kushlan, James A.; Hancock, James A. (2005). The Herons. Oxford: Oxford University Press. p. 104. ISBN 0-19-854981-4. OCLC 54913407.
  6. Scofield, R. Paul; Medway, D. G.; Chambers, Geoff K.; Gill, Brian James; Bell, Ben D.; Palma, Ricardo L.; Tennyson, Alan J. D.; Worthy, Trevor H. (2010). Checklist of the birds of New Zealand, Norfolk and Macquarie islands, and the Ross Dependency, Antarctica. Wellington: Te Papa Press. pp. 157–158. ISBN 978-1-877385-59-9.
  7. Kōtuku, the white heron
  8. "Ardea modesta - Eastern Great Egret". Species Profile and Threats Database. Canberra: Department of the Environment, Water, Heritage and the Arts, Commonwealth of Australia. February 12, 2010. Retrieved June 11, 2010.
  9. Beruldsen, Gordon (2003). Australian Birds: Their Nests and Eggs. Kenmore Hills, Qld: self. p. 184. ISBN 0-646-42798-9.
  10. Watts, Dave (2006) [1999]. Field Guide to Tasmanian Birds (2nd ed.). Frenchs Forest, NSW: New Holland Press. p. 48. ISBN 1-876334-60-6.
  11. Native Fact sheet, Kotuku Wellington Zoo Archived August 11, 2008, at the Wayback Machine
  12. Andrea Graves (May–June 2017). "Kōtuku: The story of the bird on our $2 coin". New Zealand Geographic n.145. Retrieved May 8, 2020.
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