Vertebrate Zoology: A Study Guide - T. A. Dauda 2014

Metazoans
Class Aves
Superorder Paleognathae and Neognathae - Order Anseriformes

The order Anseriformes comprises medium to large-sized waterbirds with long necks and short legs. Their feet have four digits, three of which point forward and are connected by webbed membranes. The bill is typically broad and flattened dorsoventrally. Their plumage is dense and rigid, with a well-developed downy underlayer, especially on the underside of the body. The uropygial gland is highly developed. They reproduce once a year, and their chicks are precocial.

Anseriformes are widely distributed across the globe, with approximately 200 known species. In our country, about 50 species are regular breeding representatives of this order, including swans, geese, and ducks.

Swans are the largest birds in the order, featuring very long necks that equal or exceed the length of their bodies. In flight, these birds make slow, powerful wingbeats, and they take off from the Water only after a running start. They are strong swimmers but do not dive. Juveniles form flocks, whereas adults form lifelong pairs. They nest in remote areas on large lakes and river channels overgrown with aquatic vegetation. The clutch contains up to 5–7 eggs. Only the female incubates the eggs, while the male grazes nearby. Swans feed on aquatic and terrestrial herbaceous vegetation. For the molting period, they gather in large flocks and are temporarily flightless as they lose their Primary and secondary flight feathers simultaneously. They acquire pure white plumage at two years of age. Swans are migratory birds; they arrive at their breeding grounds as the snow begins to melt and depart shortly before permanent snow cover sets in. Three species are found in our country: the whooper swan, the mute swan, and Bewick's (tundra) swan. The whooper swan, which inhabits the forest zone, has black legs and a bill that is mostly black. The mute swan, distributed across steppe zone waterbodies, has a red bill with a black knob at the Base of the upper Mandible. Bewick's swan resembles the whooper swan but is smaller and inhabits the tundra zone. Hunting swans is prohibited in our country.

Geese are large birds with a robust build and a long neck that nonetheless does not reach the length of the torso. All geese walk confidently and run swiftly on land, swim well, and most are capable of diving. In summer, they remain in pairs that persist for many years. In winter and during migration, they form large flocks. All of our native geese are migratory, breeding in sparsely populated regions rich in waterbodies, marshes, and damp meadows. They nest in dry locations close to water sources. Their nests are shallow depressions in the ground lined with dry grass, moss, and down that the females pluck from their own chests and bellies. The clutch contains 4–6 eggs. Only the female incubates the eggs, while the male perches nearby on his own "bachelor" nest or grazes in the vicinity. The chicks remain in the nest for no more than a day; once dry, they depart with their parents. They feed on terrestrial herbaceous vegetation. Waterbodies are used solely for drinking, resting, and during the molting season. Molting geese gather in flocks numbering in the hundreds, and sometimes thousands. During plumage replacement, the flight feathers are shed almost simultaneously, causing the birds to temporarily lose The ability to fly. Consequently, geese migrate to inaccessible waterbodies with muddy banks, secluded bays, and similar safe havens to molt. In our country, 11 species of geese are encountered; they are widely distributed and particularly numerous in the tundra. The best-known species are the greylag goose, the swan goose, the bean goose, and the lesser white-fronted goose. The first two species are the ancestors of many domestic goose breeds.

Many geese are an important game species, especially in the tundra and forest-steppe of Western Siberia.

Ducks are medium-sized waterbirds with a stout build and a relatively short neck. In most species, the bill is relatively broad. During the breeding season, males of all duck species are more brightly colored than females. Furthermore, dabbling ducks feature an iridescent speculum on their wings, whereas diving ducks typically have a white, or less commonly gray, speculum.

Duck flight is swift, characterized by frequent, powerful wingbeats. They fly in compact flocks or staggered lines. They are skilled swimmers and divers. With rare exceptions, they walk poorly on land, waddling from side to side.

Dabbling ducks prefer quiet lakes, river channels, and oxbows overgrown with aquatic vegetation, and they readily nest in marshes. Diving ducks inhabit deep rivers and lakes with sparse vegetation, as well as marine coasts. Ducks build their nests on the ground or occasionally in tree cavities. Only the female incubates the eggs. Once incubation begins, the males gather into flocks and depart for their molting grounds, where—much like geese—they lose the ability to fly. Females molt later than males. Dabbling ducks feed primarily on plant matter (shoots and leaves), occasionally consuming small invertebrates. Diving ducks prefer animal prey, feeding on Mollusks, small crustaceans, and insect larvae by diving to depths of up to 10 m.

Most duck species are migratory. They arrive at their breeding grounds after the ice breaks up and depart before the waterbodies freeze over. They winter in flocks on ice-free rivers and lakes, as well as in marine environments, including the Caspian Sea.

Russia is home to about 40 species of ducks. Dabbling ducks include the mallard—the ancestral form of many domestic duck breeds (Fig. 43)—the gadwall, and the northern pintail, among others. Diving ducks include the common pochard, the tufted duck, the common goldeneye, and several species of eiders. The majority of these species are important game birds.

Class="center">

Fig. 43 Ancestors of various agricultural poultry species:

1 — red junglefowl (India); 2 — wild turkey (North America); 3 — mallard.

Harvesting eiderdown is prohibited. Instead, humans collect the warm, lightweight, and durable down from their nests, which the birds pluck from their abdominal plumage to line the nest.