Chordate Zoology - Textbook - I. V. Tsaryk - 2013

Chapter 5. SUPERCLASS TETRAPODS (TERRESTRIAL VERTEBRATES) TETRAPODA, seu QUADRIPEDA.

ANAMNIOTS (ANAMNIA) AND AMNIOTES (AMNIOTA)

5.3. CLASS AVES

5.3.3. Taxonomy and characteristics of representatives of the main orders of the class Aves

5.3.3.2. Superorder Typical, or Neognathous Birds Neognathae

5.3.3.2.12. Order Anseriformes

Includes about 150 (162) species of waterbirds ranging in weight from 200 g to 10 kg. The bill is typically more or less flattened and covered with a soft horny sheath, featuring a firm thickening at the tip. Transverse horny lamellae are located along the edges of the bill and the fleshy Tongue, forming a filtering apparatus. The legs are short, and the forward-directed toes are webbed. The muscular gizzard possesses a tough cuticle. Plumage is dense. The molt of flight feathers occurs simultaneously; therefore, these birds lose The ability to flight for 2–5 weeks. Flight is fast. They walk on land with a waddling gait. They swim exceptionally well, and some species are skilled divers. In some species, pair bonds persist until the death of one partner (swans, geese); the clutch is incubated by the female, while the male guards the nesting territory, and both parents tend the brood. In many duck species, pairs form only for the breeding season, with only the female incubating and tending the brood, whereas the males gather in flocks and migrate to molting areas. Nests are built near Water bodies on the ground, and occasionally in tree hollows. Hatchlings emerge covered in dense down, and by the next day, they run and swim well, with those of some species also diving. They feed independently; the adult bird merely defends the chicks and occasionally broods them. Outside the breeding season, they congregate in small flocks.

A group uniting geese and swans, comprising 21 species. These are birds weighing from 1 to 10 kg. Males and females share identical plumage coloration. They feed predominantly on plant matter on land and in shallow water. The whooper swan Cygnus cygnus nests on large, overgrown water bodies.

The family Anatidae unites about 120 species. Males are larger than females and feature brighter coloration (Fig. 5.45, 12). River ducks are the most widespread, nesting near all types of water bodies. Their weight ranges from 200 g to 1.5 kg. They feed on a diverse diet, filtering water and silt, straining invertebrates, and consuming shoots and soft rhizomes of aquatic plants, as well as gathering acorns and fallen seeds on land. When foraging, they do not dive, but submerge only their neck and the forepart of the body. Nearly all species of waterfowl are game birds.