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Tadorna

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The genus *Tadorna* contains a group of large waterfowl known as shelducks. These birds belong to the tribe Tadornini within the Anatidae family. This biological family is quite large and includes ducks, geese, and swans. Shelducks are often described as being intermediate between geese and ducks. They are mid-sized birds, with many species measuring between 50 and 60 cm. Most of these birds are found in the Old World. They are also considered semi-terrestrial, meaning they spend significant time on land.

When a shelduck is in flight, its wing colors follow a very specific pattern. This pattern helps people identify them from a distance. The tertiary remiges, which are specific flight feathers, form a green speculum. A speculum is a bright, colored patch on the wing. The secondaries and primaries are black. Additionally, the coverts, or the feathers covering the forewing, are white. These distinct colors make their movement through the sky quite easy to recognize.

Shelducks have a varied diet that supports their life on land and near water. They consume many different types of food to stay healthy. Their diet includes various grasses and other types of plants. They also hunt for small animals found along the shore. This includes eating creatures like crabs and winkles. This mix of plant and animal matter allows them to thrive in many environments.

Scientists have studied the classification of these birds for many years. The genus *Tadorna* was officially introduced by the German zoologist Friedrich Boie in 1822. The name *Tadorna* itself comes from the French word *Tadorne*. This French term is used for the common shelduck. Some believe the name might actually come from Celtic roots. In those roots, it may have meant "pied waterfowl." Historically, these birds were often called "sheldrakes." This name was the most common term until the late 19th century.

There are many different species within this group. The common shelduck is the type species for the genus. Other living species include the Ruddy shelduck, the South African shelduck, and the Australian shelduck. The Paradise shelduck is another member of the group. Some species are no longer with us today. The Rēkohu shelduck became extinct on the Chatham Islands after the 16th century. The Crested shelduck may also be extinct, as it was last seen in the late 20th century.

Understanding how shelducks relate to other birds is a complex task for biologists. The genus *Tadorna* is very close to the Egyptian goose. It is also related to the extinct *Alopochen* birds from the Madagascar region. While most classical shelducks form a single group, some relationships are hard to define. Scientists used mtDNA cytochrome b sequence data to study these links. This molecular data showed that the relationships between certain shelducks and the Egyptian goose were poorly resolved. Because of this, the genus may be considered paraphyletic.

Even the history of these birds includes interesting fossils. Some fossil bones were found in Dorkovo, Bulgaria. These bones were originally described as *Balcanas pliocaenica*. Some researchers have suggested these bones might belong to the *Tadorna* genus. Others have proposed they might belong to the common shelduck. However, because these bones are from the Early Pliocene, that idea is unlikely. These scientific debates help us understand how waterfowl have changed over millions of years.

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