Oca egiziana

Identificazione

It swims well and appears heavy in flight, more like a goose than a duck, hence the English name. On average, they are 63–73 cm (25–29 in) tall.<p>The sexes of this species are identical in plumage but the males are usually somewhat larger. They vary greatly in plumage tone, with some birds greyer and others browner, but this variation has not been observed to be sex- or age-related. A large part of the wings of mature birds is white, but the white is hidden by the wing coverts when at rest. When it is aroused, either in alarm or aggression, the white is displayed.<p>Egyptian geese in the wild can live for up to 15 years, while captive individuals have been recorded reaching an age of 35.<p>The voices and vocalisations of the sexes differ, the male having a hoarse, subdued duck-like quack which seldom sounds unless it is aroused, as well as a louder, breathy call which is performed in a rapid sequence, sounding somewhat like a steam engine. The female has a far noisier raucous quack that frequently sounds in aggression when tending her young. The male Egyptian goose attracts its mate with an elaborate, noisy courtship display that includes honking, neck stretching and feather displays.

Tassonomia

The Egyptian goose is believed to be most closely related to the shelducks (genus Tadorna) and their relatives, and is placed with them in the subfamily Tadorninae. It is the only extant member of the genus Alopochen, which also contains closely related prehistoric and recently extinct species. mtDNA cytochrome b sequence data suggest that the relationships of Alopochen to Tadorna need further investigation.

Nome scientifico

Alopochen aegyptiaca

Autorità

(Linnaeus, 1766)

Ordine

Anseriformi

Famiglia

Anatidae

Genere

Alopochen

Areale e habitat

The Egyptian goose is native to Sub-Saharan Africa and the Nile Valley, where it is widespread and common to abundant, though it has become scarce in the northern Nile Valley. It is found in open or semi-open habitats, typically near fresh water, ranging from lowlands to 4,000 m (13,000 ft) above sea level in the Ethiopian Highlands, and largely absent from dense forests and deserts. While not breeding, it disperses somewhat, sometimes making longer migrations northwards into the arid regions of the Sahel, and occasionally even reaching the North African nations of Algeria and Tunisia, historically a more frequent part of its range.<p>It was found in southeastern Europe (up to the lower Danube Valley and southern Hungary) until the early 1700s, and in parts of Turkey and the western Middle East until the early 1900s (and has since re-established through escaped captives), but its historical ranges in these places is incompletely known and the reason for the disappearances is also unknown.<p>The British populations of the Egyptian goose date back to the 17th century when it was introduced to estates and parks, though the species was only formally added to the British bird list in 1971. The British introductions were the first outside its native range; however, these individuals did not spread widely and are not known to have expanded into other countries. In Great Britain, it is found mainly in East Anglia, and in various locations along the River Thames, where it breeds at sites with open water, short grass and suitable nesting locations (either islands, holes in old trees or amongst epicormic shoots on old trees). During the winter, they are widely dispersed within river valleys, where they feed on short grass and cereals. In the United Kingdom in 2009, it was officially declared a non-native species. Accordingly, Egyptian geese in Great Britain may be shot without special permission if they cause problems.<p>The Egyptian goose was first introduced to the Netherlands in 1967 and to Belgium in 1982, and these formed the basis for the population in mainland Europe, likely supplemented by some captive escapees from other European countries. From these two countries, the species has experienced a relatively fast range expansion into adjacent countries, first spreading into Germany and France (where possibly supplemented by local escapees) in the mid-1980s, and then to the Czech Republic, Denmark, Luxembourg and Switzerland in the early 2000s. Further observations, sometimes also involving isolated cases of breeding, have been made in Austria, Italy, Poland, Spain, Sweden and elsewhere in mainland Europe, but it is not yet known to have become established in those countries.<p>Because of its aggressiveness towards other birds, it may reduce or displace native species, and since 2017 the Egyptian goose has been listed as an invasive species in the European Union. This implies that this species cannot be imported, bred, transported, commercialized, used, exchanged or intentionally released into the environment and member states are obliged to try to eradicate the species.<p>In addition to Europe, the Egyptian goose has been introduced and established breeding populations in Mauritius, Israel, the United Arab Emirates and the United States. In the US, breeding populations are found in Arkansas, California, Florida, Nebraska, Oklahoma and Texas, with occasional reports of the species elsewhere. Although the Egyptian goose was introduced to Australia and New Zealand, it did not become established in these countries.

Migrazione

Specie stanziale

Comportamento

Comportamento migratorio: Specie stanziale.

Conservazione

Tendenza della popolazione: in diminuzione.

Tendenza della popolazione

in diminuzione