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Great egret

From Wikipedia, the free encyclopedia
(Redirected from Casmerodius)
For the short story by Sarah Orne Jewett, see A White Heron.
For the eastern populations of this species, see Eastern great egret.
Not to be confused with the all-white population of the great blue heron.

Great egret
Adult in breeding plumage in Cape May County, New Jersey
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Pelecaniformes
Family: Ardeidae
Genus: Ardea
Species:
A. alba
Binomial name
Ardea alba
Range of A. alba (excluding A. a. modesta)
  Breeding range
  Year-round range
  Wintering range
Synonyms
  • Herodias egretta Boie, 1822
  • Casmerodius egretta Gloger, 1842
  • Casmerodius albus Oberholser, 1919
  • Egretta alba (Cramp and Simmons, 1977)

The great egret (Ardea alba), also known as the common egret, large egret, or (in the Old World) great white egret[2] or great white heron,[3][4][5] is a large, widely distributed egret. The four subspecies are found in Asia, Africa, the Americas, and southern Europe. Recently, it has also been spreading to more northern areas of Europe. Distributed across most of the tropical and warmer temperate regions of the world, it builds tree nests in colonies close to water.

Taxonomy

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The great egret was formally described in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae under the binomial name Ardea alba. He specified the type locality as Europe.[6][7] The scientific name comes from Latin ardea, "heron", and alba, "white".[8]

Like all egrets, it is a member of the heron family, Ardeidae. Traditionally classified with the storks in the Ciconiiformes, the Ardeidae are closer relatives of pelicans and belong in the Pelecaniformes, instead. The great egret—unlike the typical egrets—does not belong to the genus Egretta, but together with the great herons is today placed in Ardea. In the past, however, it was sometimes placed in Egretta or separated in a monotypic genus Casmerodius.

The Old World population is often referred to as the "great white egret". This species is sometimes confused with the great white heron of the Caribbean, which is a white morph of the closely related great blue heron.

Subspecies

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Four subspecies are found in various parts of the world, which differ but little.[9] Differences among them include bare-part coloration in the breeding season and size. The smallest subspecies, A. a. modesta, is from Asia and Australasia and some taxonomists consider it to be a full species, the eastern great egret (Ardea modesta), but most scientists treat it as a subspecies.[9]

Description

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Adult In flight (California, USA)
Breeding plumage (Karnataka, India)

The great egret is a large heron with all-white plumage. Standing up to 1 m (3.3 ft) tall, this species can measure 80 to 104 cm (31 to 41 in) in length with a wingspan of 131 to 170 cm (52 to 67 in).[10][11] Body mass can range from 700 to 1,500 g (1.5 to 3.3 lb), with an average around 1,000 g (2.2 lb).[12] It is thus only slightly smaller than the great blue or grey heron (A. cinerea). Apart from size, the great egret can be distinguished from other white egrets by its yellow bill and black legs and feet, though the bill may become darker and the lower legs lighter in the breeding season. In breeding plumage, delicate ornamental feathers are borne on the back. Males and females are identical in appearance; juveniles look like nonbreeding adults. Differentiated from the intermediate egret (Ardea intermedia) by the gape, which extends well beyond the back of the eye in case of the great egret, but ends just behind the eye in case of the intermediate egret.

Its flight is slow with its neck retracted. This is characteristic of herons and bitterns, and distinguishes them from storks, cranes, ibises, and spoonbills, which extend their necks in flight. The great egret walks with its neck extended and wings held close. The great egret is not normally a vocal bird; it gives a low, hoarse croak when disturbed, and at breeding colonies, it often gives a loud croaking cuk cuk cuk and higher-pitched squawks.[13]

Sharing space on a log with a grey heron (Ardea cinerea), Oriental darter (Anhinga melanogaster) and a group of little cormorants (Microcarbo niger) (Karnataka, India)

Owing to its wide distribution across so much of the Americas, as well as Africa, Europe and Asia, the great egret shares its habitat with many other similar species. For example, the little egret (Egretta garzetta), intermediate egret (Ardea intermedia), Chinese egret (Egretta eulophotes), and the western reef heron (Egretta gularis). In the Americas, the snowy egret (Egretta thula)—a medium-sized heron that shares the same habitat as the great egret—is one such species. The snowy egret is readily distinguished from the great egret because it is noticeably smaller, and it has a more slender bill which is black in color and yellow feet, whereas the great egret has a yellow bill and black feet. Another species that—in North America—is easily confused with the great egret is the white morph of the great blue heron (Ardea herodias). The great blue heron is a bit larger, and has a thicker bill than that of the great egret.[14]

Distribution and habitat

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Non-breeding adult wading near a crocodile (Karnataka, India)

The great egret is generally a very successful species with a large and expanding range, occurring worldwide in temperate and tropical habitats. It is ubiquitous across the Sun Belt of the United States and in the Neotropics.[1]

Conservation

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In North America, large numbers of great egrets were killed around the end of the 19th century so that their plumes, known as "aigrettes", could be used to decorate hats.[15][16] Numbers have since recovered as a result of conservation measures. Its range has expanded as far north as southern Canada. However, in some parts of the southern United States, its numbers have declined due to habitat loss, particularly wetland degradation through drainage, grazing, clearing, burning, increased salinity, groundwater extraction and invasion by exotic plants. Nevertheless, the species adapts well to human habitation and can be readily seen near wetlands and bodies of water in urban and suburban areas.[1]

The great egret is partially migratory, with northern hemisphere birds moving south from areas with colder winters. It is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.[citation needed]

In 1953, the great egret in flight was chosen as the symbol of the National Audubon Society, which was formed in part to prevent the killing of birds for their feathers.[17][18]

On 22 May 2012, a pair of great egrets was observed nesting in the UK for the first time at the Shapwick Heath nature reserve in Somerset.[19] The species was a rare visitor to the UK and Ben Aviss of the BBC stated that the news could mean the UK's first great egret colony had become established.[19][20] The following week, Kevin Anderson of Natural England confirmed a great egret chick had hatched, making it a new breeding bird record for the UK.[21] In 2017, seven nests in Somerset fledged 17 young,[22] and a second breeding site was announced at Holkham National Nature Reserve in Norfolk where a pair fledged three young.[23] In January 2021, BirdGuides, a UK website and magazine which reports sightings of rare birds, dropped the species from its list of nationally rare birds because sightings had become so numerous.[24] In August 2024, RSPB Scotland announced that a pair had raised three chicks at their Loch of Strathbeg nature reserve in North Aberdeenshire, the first chicks to hatch in Scotland.[25]

A similar move northwards has been observed in the Nordic countries where historically it was only a rare visitor. The first confirmed breeding in Sweden was 2012 and in Denmark was 2014. Both countries now have small colonies.[26][27] In 2018, a pair of great egrets nested in Finland for the first time, raising four young in a grey heron colony in Porvoo.[28]


Ecology

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Egg, Collection Museum Wiesbaden

The species breeds in colonies in trees close to large lakes with reed beds or other extensive wetlands, preferably at height of 10–40 feet (3.0–12.2 m).[13] It begins to breed at 2–3 years of age by forming monogamous pairs each season. Whether the pairing carries over to the next season is not known. The male selects the nest area, starts a nest, and then attracts a female. The nest, made of sticks and lined with plant material, could be up to 3 feet across. Up to six bluish green eggs are laid at one time. Both sexes incubate the eggs, and the incubation period is 23–26 days. The young are fed by regurgitation by both parents and are able to fly within 6–7 weeks.[29]

Diet

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Spearing a fish
Landing in Matadero Creek

The great egret forages in shallow water or in drier habitats, feeding mainly on fish, frogs, other amphibians,[30] small mammals (such as mice),[31] and occasionally small reptiles (such as snakes),[31] crustaceans (such as crayfish)[32] and insects (such as crickets and grasshoppers).[31] This species normally impales its prey with its long, sharp bill by standing still and allowing the prey to come within the striking distance of its bill, which it uses as a spear. It often waits motionless for prey or slowly stalks its victim.

Parasites

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A long-running field study (1962–2013) suggested that the great egrets of central Europe host 17 different helminth species. Juvenile great egrets were shown to host fewer species, but the intensity of infection was higher in the juveniles than in the adults. Of the digeneans found in central European great egrets, numerous species likely infected their definitive hosts outside of central Europe itself.[33]

In culture

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Taxidermied specimens, American Museum of Natural History
Great Egret capturing and swallowing a fish (partially slowed video).

The great egret is depicted on the reverse side of a 5-Brazilian reais banknote.[34]

The great egret is the symbol of the National Audubon Society.[35]

An airbrushed photograph of a great egret in breeding plumage by Werner Krutein is featured in the cover art of the 1992 Faith No More album Angel Dust.[36]

In Belarus, a commemorative coin has the image of a great egret.[37] The great egret also features on the New Zealand $2 coin and on the Hungarian 5-forint coin.[38]

See also

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References

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  1. ^ a b c BirdLife International (2019). "Ardea alba". IUCN Red List of Threatened Species. 2019: e.T22697043A155465940. doi:10.2305/IUCN.UK.2019-3.RLTS.T22697043A155465940.en. Retrieved 19 November 2021.
  2. ^ "Great White Egret Facts | Ardea alba". The RSPB.
  3. ^ Bewick, Thomas (1809). "The Great White Heron (Ardea alba, Lin. – Le Heron blanc, Buff.)". Part II, Containing the History and Description of Water Birds. A History of British Birds. Newcastle: Edward Walker. p. 52.
  4. ^ Bruun, B.; Delin, H.; Svenson, L. (1970). The Hamlyn Guide to Birds to Britain and Europe. London. p. 36. ISBN 0753709562.{{cite book}}: CS1 maint: location missing publisher (link)
  5. ^ Ali, S. (1993). The Book of Indian Birds. Bombay: Bombay Natural History Society. ISBN 0195637313.
  6. ^ Linnaeus, Carl (1758). Systema Naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis (in Latin). Vol. 1 (10th ed.). Holmiae (Stockholm): Laurentii Salvii. p. 144.
  7. ^ Mayr, Ernst; Cottrell, G. William, eds. (1979). Check-List of Birds of the World. Vol. 1 (2nd ed.). Cambridge, Massachusetts: Museum of Comparative Zoology. p. 203.
  8. ^ Jobling, James A (2010). The Helm Dictionary of Scientific Bird Names. London: Christopher Helm. pp. 37, 54. ISBN 978-1-4081-2501-4.
  9. ^ a b Gill, Frank; Donsker, David; Rasmussen, Pamela, eds. (December 2023). "Ibis, spoonbills, herons, Hamerkop, Shoebill, pelicans". IOC World Bird List Version 14.1. International Ornithologists' Union. Retrieved 9 February 2024.
  10. ^ "Great Egret". All About Birds. Cornell Lab of Ornithology. Retrieved 25 September 2013.
  11. ^ "Animal Bytes – Egrets". Seaworld. Archived from the original on 21 June 2013. Retrieved 25 September 2013.
  12. ^ Dunning Jr., John B., ed. (1992). CRC Handbook of Avian Body Masses. CRC Press. ISBN 978-0-8493-4258-5.
  13. ^ a b "Great Egret". Audubon Guide to North American Birds. July 10, 2016.
  14. ^ "Similar Species for Great Egret". All About Birds. Ithaca, New York: Cornell Lab of Ornithology. 2021. Retrieved 19 March 2021.
  15. ^ Souder, William. "How Two Women Ended the Deadly Feather Trade". Smithsonian Magazine. Retrieved 2021-01-08.
  16. ^ "Aigrette definition and meaning | Collins English Dictionary". www.collinsdictionary.com.
  17. ^ "Timeline of Accomplishments". National Audubon Society. Archived from the original on 2 January 2013. Retrieved 6 March 2011.
  18. ^ "Historical Highlights: Signature Species". National Audubon Society. Archived from the original on 30 March 2009. Retrieved 6 March 2011.
  19. ^ a b Aviss, Ben (22 May 2012). "Great white egrets nest in UK for first time". BBC Nature. BBC. Retrieved 31 May 2012.
  20. ^ Aviss, Ben (31 May 2012). "Great white egrets breed in UK for first time". BBC Nature. BBC. Retrieved 31 May 2012.
  21. ^ Hallett, Emma (31 May 2012). "Rare great white egret chick hatches in UK for first time". The Independent. Independent Print Limited. Retrieved 31 May 2012.
  22. ^ Adrian Pitches (2017). "England's Mediterranean Breeding Season". British Birds. 110 (9): 430.
  23. ^ "Great White Egret breeds successfully in Norfolk for the first time". Rare Bird Alert. Retrieved 15 September 2017.
  24. ^ "Great white egret no longer rare bird as numbers boom across UK and Europe". The Independent. January 4, 2021.
  25. ^ Forbes, Ellie (22 August 2024). "Great White Egrets successfully fledge in Scotland for the first time". Scottish Field. Retrieved 22 August 2024.
  26. ^ "Første danske koloni af den sjældne sølvhejre opdaget". Dansk Ornitologisk Forening. 1 June 2017. Retrieved 29 June 2022.
  27. ^ Aronsson, N. (2019). "Snabb framryckning av flera arter i landet". Vår Fågelvärld. 6. ISSN 2002-8717.
  28. ^ "Jalohaikara pesi ensimmäistä kertaa Suomessa – Porvoossa haudotut poikaset lennähtivät maailmalle". Yle Uutiset (in Finnish). 7 August 2018. Retrieved 2018-08-11.
  29. ^ "Great Egret". All about birds, Cornell Lab of Ornithology. Cornell Lab of Ornithology. Retrieved July 10, 2016.
  30. ^ "Ardea alba (Great Egret_" (PDF). The Online Guide to the Animals of Trinidad and Tobago. University of the West Indies. Retrieved 6 August 2022.
  31. ^ a b c "Ardea alba (Great egret)". Animal Diversity Web.
  32. ^ Jones, J. (2002). "Ardea alba: great egret". Animal Diversity Web. University of Michigan. Retrieved 14 January 2022.
  33. ^ Sitko, J.; Heneberg, P. (2015). "Composition, structure and pattern of helminth assemblages associated with central European herons (Ardeidae)". Parasitology International. 64 (1): 100–112. doi:10.1016/j.parint.2014.10.009. PMID 25449288.
  34. ^ "Current Banknotes - Banco Central do Brasil". www.bcb.gov.br. Retrieved 2021-06-07.
  35. ^ "Great Egret (Ardea alba)". National Geographic Society. 10 June 2011. Archived from the original on January 29, 2010. Retrieved 31 May 2012.
  36. ^ Putterford, Mark (December 1992). "Faith No More - Dusted". Rip.
  37. ^ "1 Rouble, Belarus". en.numista.com. Retrieved 2021-06-07.
  38. ^ "5 Forint". Numista. Retrieved 17 May 2020.
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