3647 x 2735 px | 30,9 x 23,2 cm | 12,2 x 9,1 inches | 300dpi
Date de la prise de vue:
2 janvier 2012
Informations supplémentaires:
Picture of a amorous couple of 2 white swans. Swans feed in the water and on land. They are almost entirely herbivorous, although they may eat small amounts of aquatic animals. In the water food is obtained by up-ending or dabbling, and their diet is composed of the roots, tubers, stems and leaves of aquatic and submerged plants.[2] Swans form socially monogamous pair bonds that last for many years, and in some cases these can last for life.[4] Modern genetic techniques are starting to reveal that 'divorces' are more common than previously thought, as is mating with other swans outside of the social pairing, without breaking the social pair bond.[5] These bonds are maintained year round, even in gregarious and migratory species like the Tundra Swan, which congregate in large flocks in the wintering grounds.[6] The nest is on the ground near water and about a metre across. Unlike many other ducks and geese the male helps with the nest construction. Average egg size (for the mute swan) is 113×74 mm, weighing 340 g, in a clutch size of 4 to 7, and an incubation period of 34–45 days.[7] With the exception of the whistling ducks they are the only anatids where the males aid in incubating the eggs. [edit]Systematics and evolution All evidence suggests that the genus Cygnus evolved in Europe or western Eurasia during the Miocene, spreading all over the Northern Hemisphere until the Pliocene. When the southern species branched off is not known. The Mute Swan apparently is closest to the Southern Hemisphere Cygnus (del Hoyo et al., eds, Handbook of the Birds of the World); its habits of carrying the neck curved (not straight) and the wings fluffed (not flush) as well as its bill color and knob indicate that its closest living relative is actually the Black Swan..were mostly uninhabitable during the last ice age) a
