Great Egret
| Great Egret | ||||||||||||
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| Ardea alba | ||||||||||||
| Linnaeus , 1758 |
The Great Egret ( Ardea alba , Syn. : Casmerodius albus , Egretta alba ) belongs to the family of herons from the order Pelecaniformes . There are four subspecies.
The species has a very large distribution area that includes large parts of Eastern and Southern Europe, North, Central and South America, Asia and Africa. In Central Europe, the great egret is a locally widespread and frequent breeding and annual bird. The species shows a pronounced tendency to migrate and is observed in increasing numbers in the regions of Central Europe, in which it is not a breeding bird.
The IUCN classifies the great egret as not endangered ( least concern ). The population is estimated at 590,000 to 2,200,000 individuals.
Appearance
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The great egret is a great, white heron with a yellow beak and dark legs and feet. Its length is 85 to 100 centimeters, the wingspan is 145 to 170 centimeters, and the weight is 1 to 1.5 kilograms.
Unlike other heron species of the genera Ardea and Egretta , the great egret has no decorative feathers on the back of the head. Instead, it forms long, loose shoulder feathers with long side branches during the breeding season. During courtship, these are spread out like a wheel. The nominate form Ardea alba alba has dark greenish-gray or black legs, the iris is yellow and the beak is black with a yellow base during the breeding season. Outside the breeding season, the beak is yellow to orange-yellow. Many individuals have a darker beak tip. The bare rein and orbital ring are greenish-yellow outside the breeding season and light emerald green during the breeding season.
distribution
The great egret is the heron with the greatest geographical distribution . As a cosmopolitan he can be found on all continents except for Antarctica . In addition to the American double continent , which it colonizes from north to south Canada , it occurs in southern and central Europe , Africa , the Middle East, as well as Australia and New Zealand. In Central Europe it breeds regularly at Lake Neusiedl and since 1992 also in the Netherlands . Over a longer period of time there were several suspicions of breeding in Germany. B. 2002 on an Upper Bavarian pre-alpine lake. According to the DDA, the first reliable proof of breeding for the great egret in Germany was achieved in 2012 in the far northeast, where two pairs had settled in a gray heron colony. A breeding pair was first sighted in the UK in 2012.
Great egrets are partial migrants . From July there is an undirected dispersal of the young birds. Adult birds leave the breeding areas between September and November. However, they stay close to the breeding areas in mild winters or show winter migration later. Hibernating great egrets can be observed on Lake Constance, for example. The great egrets return to their breeding colonies in late February to early April.
habitat
The great egret lives in reed belts on lakes, rivers and oxbow lakes as well as in swamps with trees and bushes. Outside of the breeding season, it also likes to stay in large grassland areas. In Australia, it also uses extensive estuaries during this time.
food
Insects , amphibians , fish and mice are the main food of the great egret. In the Lower Rhine region, it looks for food primarily on the large grassland areas. He regularly seeks proximity to the Arctic wild geese that winter there. These eat the grass briefly, so that the silver and gray herons can hunt for mice there particularly well.
The great egret usually finds its food by wading slowly in shallow water. The body is held more or less horizontally. Alternatively, the great egret waits in a rigid posture for food animals to come within reach.
Reproduction
Great egrets live in monogamous seasonal marriage and become sexually mature in the second year of life. They breed in colonies, but also individually. The nests, up to 100 cm in size, are built close together on the ground, mostly in inaccessible reed beds. The conspicuously white colored wading birds can hardly be seen here. It also happens that the nests are placed in deep bushes. Usually in April or May 3 to 5 light blue eggs are laid every two days and are incubated by both partners from the first day. The young birds hatch after 25-26 days and are fledged at 40-50 days. Additional clutches are observed. 75% of the young birds do not survive the first year of life.
Duration
By the end of the 19th century and the beginning of the 20th century, great egrets were almost extinct in many breeding areas in Europe. This was followed by several phases in which the stocks recovered, but then declined again. These population declines were partly due to fluctuating water levels. Since the mid-1970s, the population has been increasing again in many breeding areas. Numerous new colonies were formed in Hungary, and 737 breeding pairs settled at Lake Neusiedl in 1997. There are declines in stocks, on the one hand, due to direct tracking, but also due to the loss of suitable undisturbed old reed stocks due to construction or burning of the reed areas. Disruptions caused by leisure activities can also lead to great egrets giving up breeding grounds.
The population in Germany has been increasing since around 1985. Most great egrets are seen in autumn and winter. In September and October the focus is on Brandenburg, Saxony and Bavaria, where groups of up to several hundred great egrets have been observed in Saxony and Brandenburg in recent years, especially in wetlands and ponds. During the winter months, great egrets can be observed especially in northern and western Germany, with the Lower Rhine between Duisburg and the German-Dutch border area between Kleve and Nijmegen seeming to be a focus with around 150 overwinterers. The first great egrets appear here in August and September. The largest stocks are found from October to March. Since 1992 there have been repeated reports of suspected breeding of the great egret in Germany. The first correct proof of brood was only provided in Mecklenburg in 2012. Two pairs were breeding in the gray heron colony in Niederhof am Strelasund , where breeding was suspected as early as 2009 and 2010. Two young birds were observed.
In Austria, where it hardly occurs except at Lake Neusiedl, the great egret is on the red list of endangered animal species.
literature
- Hans-Günther Bauer, Einhard Bezzel and Wolfgang Fiedler (eds.): The compendium of birds in Central Europe: Everything about biology, endangerment and protection. Volume 1: Nonpasseriformes - non-sparrow birds. Aula-Verlag Wiebelsheim, Wiesbaden 2005, ISBN 3-89104-647-2 .
- PJ Higgins (Eds.): Handbook of Australian, New Zealand & Antarctic Birds , Volume 1, Ratites to Ducks, Oxford University Press, Oxford 1990, ISBN 0-19-553068-3
Web links
- The Great Egret Picture documentation of the elegant bird
- Ardea alba in the endangered Red List species the IUCN 2007. Posted by: BirdLife International, 2008. Accessed October 19 of 2008.
- Feathers of the great egret
Individual evidence
- ↑ BirdLife Factsheet on the Great Egret , accessed April 24, 2011
- ^ Higgins, p. 970
- ↑ Christopher König, Stefan Stübing and Johannes Wahl (2012): Vögel in Deutschland aktuell: Summer 2012 - New breeding bird species and some special features . The falcon 59, p. 384.
- ↑ Great white egrets breed in UK for first time. In: BBC Nature. Retrieved June 1, 2012 .
- ↑ a b Bauer et al., P. 261.
- ^ Higgins, p. 968
- ↑ Bauer et al., P. 263
- ↑ Klaus-Dieter Feige, Mario Müller: First breeding record of the great egret Casmerodius Albus in Germany . Ornithole. Roundbr. Mecklenburg-Western Pomerania 2012/47, no. 3, pp. 258–264.