Luigi Strano
Zevio (Vr) - L'eleganza del cigno
Swans, genus Cygnus, are birds of the family Anatidae, which also includes geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe Cygnini. Sometimes, they are considered a distinct subfamily, Cygninae. There are six to seven species of swan in the genus Cygnus; in addition there is another species known as a swan, the Coscoroba Swan, although this species is no longer considered related to the true swans. Swans usually mate for life, though 'divorce' does sometimes occur, particularly following nesting failure. The number of eggs in each clutch ranges from three to eight.
The word "swan" is derived from Old English swan, akin to the German Schwan and Dutch zwaan, in turn derived from Indo-European root *swen (to sound, to sing), whence Latin derives sonus (sound).[1] Young swans are known as cygnets, from the Latin word for swan, cygnus. An adult male is a cob, from Middle English cobbe (leader of a group); an adult female is a pen.
The swans are the largest members of the duck family Anatidae, and are amongst the largest flying birds. The largest species, including the mute swan, trumpeter swan, and whooper swan, can reach length of over 60 inches and weigh up to 50 pounds. Their wingspans can be almost 10 ft (3 m). Compared to the closely related geese they are much larger in size and have proportionally larger feet and necks.[2] They also have a patch of unfeathered skin between the eyes and bill in adults. The sexes are alike in plumage, but males are generally bigger and heavier than females.
The Northern Hemisphere species of swan have pure white plumage but the Southern Hemisphere species are mixed black and white. The Australian Black Swan (Cygnus atratus) is completely black except for the white flight feathers on its wings; the chicks of black swans are light grey in colour, and the South American Black-necked Swan has a black neck.
The legs of swans are normally a dark blackish grey colour, except for the two South American species, which have pink legs. Bill colour varies: the four subarctic species have black bills with varying amounts of yellow, and all the others are patterned red and black. The Mute Swan and Black-necked Swan have a lump at the base of the bill on the upper mandible.
Whooper Swans migrate from Iceland, Scandinavia and northern Russia to Europe, Central Asia, China and JapanThe swans are generally found in temperate environments, rarely occurring in the tropics. Four (or five) species occur in the Northern Hemisphere, one species is found in Australia and New Zealand and a final species is distributed in southern South America. They are absent from tropical Asia, Central America, northern South America and the entirety of Africa. One species, the Mute Swan, has been introduced to North America, Australia and New Zealand.
Several species are migratory, either wholly or partly so. The Mute Swan is a partial migrant, being resident over areas of Western Europe but wholly migratory in Eastern Europe and Asia. The Whooper Swan and Tundra Swan are wholly migratory, and the Trumpeter Swans are almost entirely migratory.[2] There is some evidence that the Black-necked Swan is migratory over part of its range, but detailed studies have not established whether these movements are long or short range migration.
Swans feed in the water and on land. They are almost entirely herbivorous, although small numbers of aquatic animals may be eaten. 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.
Mute Swan's nest with two unhatched eggsSwans form monogamous pair bonds that last for many years. In many cases these pair bonds can last for life, but 'divorces' between pairs do occur.[4] Modern genetic techniques are starting to reveal that these divorces are more common than previously thought.[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 x 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.
Mute swans have been observed to display homosexual or transgender behavior.
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. Given the biogeography and appearance of the subgenus Olor it seems likely that these are of a more recent origin, as evidence shows by their modern ranges (which were mostly uninhabitable during the last ice age) and great similarity between the taxa.
Cigno è il nome comune di alcuni grandi, bianchi uccelli acquatici dal lungo collo flessuoso, facenti parte del genere Cygnus della famiglia degli Anatidi.
Presente con varie specie e sottospecie in tutto il mondo. Le rive dello specchio d'acqua devono essere in lieve pendio per consentire ai cigni d'entrare ed uscire agevolmente dall'acqua. Inoltre il terreno dev'essere dotato d'un prato verde dove i cigni possano "pascolare" allegramente.
Grigi alla nascita, diventano bianchi solo da adulti. Il cigno reale (Cygnus olor) si può osservare in Italia, con la sua notevole apertura alare di 200-240 cm. Il cigno selvatico (Cygnus cygnus) è presente nel Nord-Europa e sverna anche sulle coste orientali dell'Adriatico. Le dimensioni sono praticamente uguali a quelle del cigno reale. La Finlandia lo ha scelto come effigie sulle nuove monete da un Euro. Il cigno minore (Cygnus colombianus, con la sottospecie bewickii) è presente solo in Nord-Europa. Come suggerisce il nome, è più piccolo delle due specie precedenti (ca. 20% più piccolo).
Non sporca, non arreca alcun fastidio, non emette suoni se non un lieve sibilo che s'ode appena (tanto che in passato si riteneva che fosse muto). Se nel laghetto vi sono pesci, non li molesta. Difficile è invece, la sua convivenza con i consimili (come le anatre) perché ha un carattere litigioso e dispotico.
I cigni formano coppie che restano unite tutta la vita: nidificano tra i canneti, dove la femmina cova per circa un mese da 4 a 8 uova azzurrognole, mentre il maschio fa la guardia al nido. Alla nascita e fino al raggiungimento dell'età adulta i giovani cigni mantengono un piumaggio assai poco attraente (in genere d'un colore grigiastro simile a quello d'un uccello bianco passato attraverso un camino sporco di fuliggine) ma assai più mimetico - ed utile quindi alla sopravvivenza - di quello, bello ma vistoso, degli adulti.
I cigni sono uccelli essenzialmente erbivori, infatti, si nutrono in prevalenza di piante acquatiche e palustri che strappano dal fondo con il becco. Mentre la maggior parte degli uccelli acquatici deve tuffarsi sott'acqua alla ricerca del cibo, il cigno può tranquillamente esplorare la vegetazione sottostante fino ad un metro di profondità, grazie al suo lunghissimo collo. A volte "pascolano" sulla terraferma e lungo le rive cibandosi di erbe, radici e semi. In realtà la loro dieta non è strettamente vegetariana: infatti, insieme alle erbe ingurgitano anche un buon numero di piccoli animaletti acquatici ad esse associati (crostacei, larve d'insetti e lumachine). Sono poi dei grandi opportunisti, ghiotti di pane (soprattutto se inzuppato nel latte, pastoni per le anatre o destinati ad altri animali, farina d'orzo, riso cotto, biscotti, mais, patate cotte, frutti, crusca, verdure (soprattutto crude), ortaggi vari e perfino carne in minuscoli bocconi mescolati al pastone. In cattività spesso il cibo viene servito in un capiente contenitore di legno e plastica che può essere posato in terra oppure messo a galleggiare sull'acqua.
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Zevio (Vr) - L'eleganza del cigno
Swans, genus Cygnus, are birds of the family Anatidae, which also includes geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe Cygnini. Sometimes, they are considered a distinct subfamily, Cygninae. There are six to seven species of swan in the genus Cygnus; in addition there is another species known as a swan, the Coscoroba Swan, although this species is no longer considered related to the true swans. Swans usually mate for life, though 'divorce' does sometimes occur, particularly following nesting failure. The number of eggs in each clutch ranges from three to eight.
The word "swan" is derived from Old English swan, akin to the German Schwan and Dutch zwaan, in turn derived from Indo-European root *swen (to sound, to sing), whence Latin derives sonus (sound).[1] Young swans are known as cygnets, from the Latin word for swan, cygnus. An adult male is a cob, from Middle English cobbe (leader of a group); an adult female is a pen.
The swans are the largest members of the duck family Anatidae, and are amongst the largest flying birds. The largest species, including the mute swan, trumpeter swan, and whooper swan, can reach length of over 60 inches and weigh up to 50 pounds. Their wingspans can be almost 10 ft (3 m). Compared to the closely related geese they are much larger in size and have proportionally larger feet and necks.[2] They also have a patch of unfeathered skin between the eyes and bill in adults. The sexes are alike in plumage, but males are generally bigger and heavier than females.
The Northern Hemisphere species of swan have pure white plumage but the Southern Hemisphere species are mixed black and white. The Australian Black Swan (Cygnus atratus) is completely black except for the white flight feathers on its wings; the chicks of black swans are light grey in colour, and the South American Black-necked Swan has a black neck.
The legs of swans are normally a dark blackish grey colour, except for the two South American species, which have pink legs. Bill colour varies: the four subarctic species have black bills with varying amounts of yellow, and all the others are patterned red and black. The Mute Swan and Black-necked Swan have a lump at the base of the bill on the upper mandible.
Whooper Swans migrate from Iceland, Scandinavia and northern Russia to Europe, Central Asia, China and JapanThe swans are generally found in temperate environments, rarely occurring in the tropics. Four (or five) species occur in the Northern Hemisphere, one species is found in Australia and New Zealand and a final species is distributed in southern South America. They are absent from tropical Asia, Central America, northern South America and the entirety of Africa. One species, the Mute Swan, has been introduced to North America, Australia and New Zealand.
Several species are migratory, either wholly or partly so. The Mute Swan is a partial migrant, being resident over areas of Western Europe but wholly migratory in Eastern Europe and Asia. The Whooper Swan and Tundra Swan are wholly migratory, and the Trumpeter Swans are almost entirely migratory.[2] There is some evidence that the Black-necked Swan is migratory over part of its range, but detailed studies have not established whether these movements are long or short range migration.
Swans feed in the water and on land. They are almost entirely herbivorous, although small numbers of aquatic animals may be eaten. 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.
Mute Swan's nest with two unhatched eggsSwans form monogamous pair bonds that last for many years. In many cases these pair bonds can last for life, but 'divorces' between pairs do occur.[4] Modern genetic techniques are starting to reveal that these divorces are more common than previously thought.[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 x 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.
Mute swans have been observed to display homosexual or transgender behavior.
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. Given the biogeography and appearance of the subgenus Olor it seems likely that these are of a more recent origin, as evidence shows by their modern ranges (which were mostly uninhabitable during the last ice age) and great similarity between the taxa.
Cigno è il nome comune di alcuni grandi, bianchi uccelli acquatici dal lungo collo flessuoso, facenti parte del genere Cygnus della famiglia degli Anatidi.
Presente con varie specie e sottospecie in tutto il mondo. Le rive dello specchio d'acqua devono essere in lieve pendio per consentire ai cigni d'entrare ed uscire agevolmente dall'acqua. Inoltre il terreno dev'essere dotato d'un prato verde dove i cigni possano "pascolare" allegramente.
Grigi alla nascita, diventano bianchi solo da adulti. Il cigno reale (Cygnus olor) si può osservare in Italia, con la sua notevole apertura alare di 200-240 cm. Il cigno selvatico (Cygnus cygnus) è presente nel Nord-Europa e sverna anche sulle coste orientali dell'Adriatico. Le dimensioni sono praticamente uguali a quelle del cigno reale. La Finlandia lo ha scelto come effigie sulle nuove monete da un Euro. Il cigno minore (Cygnus colombianus, con la sottospecie bewickii) è presente solo in Nord-Europa. Come suggerisce il nome, è più piccolo delle due specie precedenti (ca. 20% più piccolo).
Non sporca, non arreca alcun fastidio, non emette suoni se non un lieve sibilo che s'ode appena (tanto che in passato si riteneva che fosse muto). Se nel laghetto vi sono pesci, non li molesta. Difficile è invece, la sua convivenza con i consimili (come le anatre) perché ha un carattere litigioso e dispotico.
I cigni formano coppie che restano unite tutta la vita: nidificano tra i canneti, dove la femmina cova per circa un mese da 4 a 8 uova azzurrognole, mentre il maschio fa la guardia al nido. Alla nascita e fino al raggiungimento dell'età adulta i giovani cigni mantengono un piumaggio assai poco attraente (in genere d'un colore grigiastro simile a quello d'un uccello bianco passato attraverso un camino sporco di fuliggine) ma assai più mimetico - ed utile quindi alla sopravvivenza - di quello, bello ma vistoso, degli adulti.
I cigni sono uccelli essenzialmente erbivori, infatti, si nutrono in prevalenza di piante acquatiche e palustri che strappano dal fondo con il becco. Mentre la maggior parte degli uccelli acquatici deve tuffarsi sott'acqua alla ricerca del cibo, il cigno può tranquillamente esplorare la vegetazione sottostante fino ad un metro di profondità, grazie al suo lunghissimo collo. A volte "pascolano" sulla terraferma e lungo le rive cibandosi di erbe, radici e semi. In realtà la loro dieta non è strettamente vegetariana: infatti, insieme alle erbe ingurgitano anche un buon numero di piccoli animaletti acquatici ad esse associati (crostacei, larve d'insetti e lumachine). Sono poi dei grandi opportunisti, ghiotti di pane (soprattutto se inzuppato nel latte, pastoni per le anatre o destinati ad altri animali, farina d'orzo, riso cotto, biscotti, mais, patate cotte, frutti, crusca, verdure (soprattutto crude), ortaggi vari e perfino carne in minuscoli bocconi mescolati al pastone. In cattività spesso il cibo viene servito in un capiente contenitore di legno e plastica che può essere posato in terra oppure messo a galleggiare sull'acqua.
Font : Wikipedia