Sea ducks and sawyers

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Sea ducks and sawyers
Eider pair (Somateria mollissima)

Eider pair ( Somateria mollissima )

Systematics
Class : Birds (aves)
Order : Goose birds (Anseriformes)
Family : Duck birds (Anatidae)
Subfamily : Anatinae
Tribe : Sea ducks and sawyers
Scientific name
Mergini
Rafinesque , 1815

The sea ducks and sawyers (Mergini) form a tribe of the duck birds (Anatidae). The species belonging to this tribe are very inhomogeneous both in terms of their appearance and way of life. While the sea ducks are small to large, diving ducks, most of which are at least outside the breeding season at sea, the sawducks are characterized by a pronounced specialization in fishing.

Appearance

The external appearance of the sea ducks and sawsmen is extremely inhomogeneous. While the large eider ducks tend to look a bit clumsy and clumsy, the smaller long-tailed, long-sleeve and collar ducks are more reminiscent of diving ducks . The anatomy of the sawmill can appear quite delicate due to the elongated beak, an adaptation to fishing, and the slim, relatively long neck.

Characteristic for all species of the tribes are the short and very strong legs, which often start far in the back third of the body, and the feet with large webbed feet, which ensure an effective drive when diving. On land, most species look very clumsy due to their anatomy. As with many species of goose birds , sea ducks and sawdaws also have a pronounced sexual dimorphism , which is particularly noticeable in the king eider . The males often have spectacular plumage, whereas the females usually appear inconspicuously brown or gray. In order to adapt to the preferred food, all sea ducks have a more or less strong and wide beak, the sawaways, on the other hand, are characterized by the eponymous sawn beak, which makes it easier for them to fish.

Diet and Lifestyle

The majority of the diet of sea ducks and sawsaws consists of animal food, most of which is captured by diving. Eider ducks in particular, as well as the species of the genus Melanitta, are pronounced food specialists, as they almost exclusively eat mussels and snails, although algae are also consumed. When looking for food, great depths are sometimes sought, although a large part of the feed organisms is sought in the shallower bank area of ​​the waters. The fish-eating sawaws are also specialized, but they also occasionally eat small animals and seeds as well as aquatic plants. The diet of the other members of the tribe also consists of crustaceans, mollusks and other invertebrates, as well as vegetable foods in varying degrees. The diet can differ depending on the season and location (sea or fresh water) of a species.

Outside the breeding season, the sea ducks in particular live strictly marine, in winter many species form large flocks off the coast. Some sawyers as well as species of the genus Bucephala overwinter both on coasts and on larger and nutrient-rich waters inland. Although they are not bad fliers, many sea ducks and sawdaws appear clumsy even in flight and usually avoid escaping into the air in danger, but try to escape by diving. The species of the tribes fly with rapid wing beats and need a fairly large run-up over the water to take off before they can rise into the air.

distribution

17 of the 20 known species of the tribe live in the northern hemisphere, only one species, the Darksaw , lives in the southern hemisphere. Within the range, many of the species are found as breeding birds on the northern coasts and lakes of the Eurasian and American continents, while some species also spend the winter on subtropical coasts.

Reproduction

There are also big differences within the tribe with regard to the breeding behavior. Eider ducks as well as long-tailed ducks and the genus Melanitta are breeding birds partly in high arctic tundras and boreal forests, where they usually breed in pairs or in loose associations near small bodies of water. The nest often consists of nothing more than a natural hollow, which is padded with down and grass. Some species of golden-bellied and sawtooth are cave-breeders and as such often nest far inland in forests near waters, occasionally artificial breeding devices are also adopted. The non-cave-breeding species lay their grass and down nest hidden under vegetation. Collared ducks breed near fast flowing waters of the highlands, their nest resembles that of the eider ducks.

Danger

Of the 20 species of Mergini, 15 are considered not endangered, the world populations usually include several hundred thousand individuals. However, some species still suffer from the loss of habitat and breeding opportunities, especially the cave-nesting tribes. In winter, during the stay at sea, the sea ducks, which are usually found in large flocks, are endangered by pollution of the sea by oil.

Relatively little information is available about the size of the Darksawer population , so classification is difficult. However, due to the relatively small distribution area and the rapid destruction of the habitat, it can be assumed that the species has declining population numbers, especially since it has not yet been observed in large numbers anywhere. Therefore, the species is classified as critically endangered.

The scaled sawmill is endangered because the already small population of a few thousand individuals is threatened by hunting and the loss of the habitat.

When threatened , the true eider because the observed population in Alaska has declined significantly. The exact causes of this decline are not known, and a natural fluctuation in population size cannot be completely ruled out.

Two species, the labrador duck and the Aucklandsäger, are considered extinct. Chendytes lawi is a prehistoric species that became extinct in the early Holocene.

Systematics

In addition to the extinct species mentioned above, sea ducks and sawdaws include the following 20 species from nine genera :

swell

Web links

Commons : Sea Ducks and Sawyers  - Album with pictures, videos and audio files