There are six to seven species of swan in the genus Cygnus - which likely evolved in Europe or western Eurasia during the Miocene, spreading all over the Northern Hemisphere until the Pliocene.
The male is called a "cob" - from Middle English cobbe (leader of a group); the female "pen," and their chicks are known as "cygnets" - from the Latin word for swan, cygnus.
Swan pairs typically bond for life and pairs stay together throughout the year, including moving together in migratory populations. However, it has been observed that some of them switch mates over their lifetimes, particularly after nesting failures, and some that lost their mate did not mate again. The "divorce rate" is estimated to be about 6%. Additionally, studies found that around a third of all broods exhibit extra-pair paternity.
If a male pairs up with another younger female, she will typically join him on his territory. If he pairs up with an older female, he will go to hers. If a female loses her mate, she will usually pair up quickly - usually choosing a younger male. Bonded pairs tend to remain together year-round; however, outside the breeding season, they are highly social and often congregate with large numbers of other swans. During the breeding season, pairs will, however, aggressively defend their territories.
Typical swans perform what is commonly referred to as "triumph ceremony" referencing the male's performance after successfully challenging a rival suitor. This ceremony involves posturing and calling.
Sometimes, it is easy to confuse geese and the related ducks and swans, and the groupings are in some cases unclear and disputed. However, speaking in general terms, size is usually a method of identification: swans tend to be larger than true geese and ducks are usually smaller.
The swans are amongst the largest flying birds.
The largest species, including the mute swan, trumpeter swan, and whooper swan, can reach a length of over 1.5 m (60 inches) and weigh over 15 kg (33 pounds). Their wingspans can be almost 3 m (10 ft). Compared to the closely related geese they are much larger in size and have proportionally larger feet and necks. 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.
Swans occurring in the Northern Hemisphere have a white plumage, while those found in the Southern Hemisphere have a black and white plumage.
The Australian Black Swan (Cygnus atratus) is completely black except for the white flight feathers on its wings. It has been noted that the Australian black swan only swims with one leg, tucking the other leg above its tail. The reason for this may be that the swan can more easily change direction when swimming on the surface of the water, if needed to escape an oncoming predator or to more quickly get to food.
The legs of swans are mostly dark black - except two South American species have flesh-colored legs.
Beak colorations range from entirely black bills, to black with varying amounts of yellow, or patterned red and black. The Mute Swan and Black-necked Swan have a noticeable knob at the base of the bill on the upper beak.
The swans rarely occur in the tropics and are absent from tropical Asia, Central America, northern South America and the entirety of Africa.
The Mute Swan has been introduced to North America, Australia and New Zealand.
Several species are migratory or partly migratory, while some populations are resident..
- Subgenus Cygnus
- Subgenus Chenopis
- Subgenus Sthenelides
- Black-necked Swan, Cygnus melancoryphus of South America.
- Subgenus Olor
- Whooper Swan, Cygnus cygnus breeds in Iceland and subarctic Europe and Asia, migrating to temperate Europe and Asia in winter.
- Trumpeter Swan, Cygnus buccinator is the largest North American swan. Very similar to the Whooper Swan (and sometimes treated as a subspecies of it), it was hunted almost to extinction but has since recovered.
- Tundra Swan, Cygnus columbianus is a small swan which breeds on the North American tundra, further north than Trumpeter Swan. It winters in the USA.
Swans breed in freshwater marshes, ponds, lakes and along slow-flowing rivers.
Most Swans find their mates before the age of 2 years - usually during the winter season. Even though some may nest for the first time when they are two years old, most won't start until they are 3 to 7 years old.
Swans are believed to form lifelong pair bonds. However, if one mate dies, the survivor will find another mate. Mute swans have been observed to display homosexual or transgender behavior.
Upon arrival in the breeding territory, the pair will engage in courtship behavior, which includes bobbing their heads and facing each other with quivering wings.
Nesting usually occurs from April through July.
They will nest in areas with ample food supply, shallow and uncontaminated water, and few disturbances. Usually, only one pair nests on a single body of water. These nesting territories range from 6 to 150 acres in size and are often located near where the female was hatched. The female chooses the nesting area, while the male defends it. Swan pairs are most likely to return to the same nesting site if they were able to raise young successfully there in the past.
The Swan's nesting season is timed to take advantage of readily available food supplies.
Nest sites are often situated on slightly elevated sites surrounded by water, such as on top of old beaver houses, dams or muskrat mounds; on emergent vegetation that is either floating or anchored to the bottom of the water; or on small islands. Pairs will either build a new nest or repair the nest that they have used in previous years.
Nest-building begins in mid-April and may take up to two weeks. The male uproots aquatic vegetation, grasses and sedges, and transfers it to the female, who will first pile it up high and then uses her body to form a depression to place her eggs in. It's basically shaped like a large open bowl. The interior is lined with down and feathers. Once completed, the nests may reach a diameter of up to 11.5 feet (1 to 3.5 meter). The nest is often surrounded by a 20 to 30 foot (6 to 9 meter) ditch - usually filled with water to make it more difficult for mammalian predators to access the nest.
Eggs / Incubation
Beginning in late April to June, the female usually starts laying eggs - often before the nest is even completed. Eggs are laid every other day until the clutch is complete. The average clutch consists of 2 to 10 creamy white eggs, but in most cases 5. If it is the female's first clutch, she is likely to lay fewer eggs and these eggs are more likely to be infertile. An Trumpeter Swan's egg is about 2.9 in (73 mm) wide and 4.5 in (113.5 mm) long; and weighs about 11.3 oz or 320 g. A Mute Swan's egg is about 113 x 74 mm and weighs 340 g.
Once a clutch is complete, the female incubates the eggs for about 32 to 45 days, while the male remains nearby to defend the nest against intruders and predators. Very rarely, the male may help brooding the eggs. During the incubation period, the female leaves the nest only for short periods to feed on nearby vegetation, bathe and preen her feathers - however, before doing so, she usually covers the eggs with nesting material to conceal them. The male will also remain nearby to deter predators.
The parents usually perform a "victory display" after intruders are deterred - which is similar to their courtship display and consists of facing each another while quivering their wings and trumpeting loudly. They may lay a second clutch if the first eggs or cygnets are lost.
Swan chicks are commonly referred to as cygnets. Hatching usually occurs from June to July. The hatchlings are covered with down and their eyes are open. Within 24 hours of hatching, the cygnets are able to leave the nest and another day later, they are able swim and dive under water to escape danger. The cygnets weigh only about 7 - 10.5 ounces (~ 200 - 300 grams) when they hatch; but grow quickly gaining 20% of their body weight every day at the early stages. By the time they take their first flight they weigh about 15.5 pounds (7 kilograms).
Both parents feed and protect the young. For the first weeks after hatching, the parents will intermittently brood the cygnets during poor weather and cold spells.
Typical Swans (genus Cygnus) are often seen carrying cygnets on their back.
When the cygnets are about two weeks old, they are able to feed themselves, mostly taking aquatic insects and crustaceans (such as crabs, lobsters, crayfish, shrimp, krill and barnacles). Even though the adult swans only eat plant matter, cygnets initially concentrate on protein-rich insects to support their rapid growth. By the time the cygnets are 4 to 6 weeks old, they start changing over to a plant-based diet. By the time they are 2 to 3 months, their diet is similar to the adults' -- mostly consisting of leaves, stems, tubers, and roots of aquatic plants.
When they are 4 weeks old, the shoulder (scapular), tail and flank feathers are replacing the feather down. At six weeks, the under plumage and cheeks are fully feathered. By seven weeks, they have most neck and head feathers. They are usually fully feathered when they are about 9 - 10 weeks old.
By the time they are 8 to 10 weeks old, they have reached half their adult size and have the juvenile grey plumage that they retain until their second winter.
By the time they are 13 to 17 weeks old, the cygnets weigh about 20 pounds (9 kg) and they learn to fly. Fledglings usually remain close to their parents for continued protection and brooding until the next spring.
In late September, the young swans take daily practice flights in preparation for the winter migration. These flights are initially short, but get longer as the young grow stronger.
Just before the water begins to freeze, they will migrate south to the wintering areas. Family groups and mated pairs usually stick to themselves. The immature swans remain with their parents throughout the winter and migrate with them to their breeding territory in spring. The cygnets are about one year old then, and the parents drive them away as they are getting ready for nesting.
The young swans remain together in sibling groups until they are about two years old, at which time, they themselves commence their search for mates. Some may return to their parents after the breeding season. Their family bonds are generally strong.
What they eat ...
Swans feed primarily on aquatic plants; but they also eat grain, grasses and crop foods, such as wheat, potatoes and carrots - especially in the winter when other food sources aren't readily available.
Only young cygnets (immature swans) eat aquatic insects and crustaceans, as they have a higher requirement for protein than the adults. As they get older, their diet changes over to a plant diet, which includes aquatic vegetation and roots.
How they eat ...
In shallow water, Swans may use their strong webbed feet to dig into submerged mud and, like mallards, they tip up - plunging the head and neck underwater - to expose and feed on roots, shoots and tubers. Cygnets feed on invertebrates and aquatic vegetation stirred up by their foraging parents. Ducks and other water birds also often follow swans to forage on exposed plant mattter and aquatic insects.,
Their long necks give them an advantage over the short-necked ducks, as they can feed in deeper waters than geese or ducks. They can feed in waters that are up to 4 feet (1.2 meters) deep by uprooting plants and snapping off the leaves and stems of plants growing underwater.
Swans also forage by swimming picking up plant material from the water's surface or water's edge. On land, they feed on grains and grasses.
Their calls consist of a loud, deep, sonorous, trumpet-like honking sounds, as well as peeps, hisses and gurgles.
Their loud calls carry for a great distance.
Swans are known to live 20 to 30 years. Swans form pair bonds when they are two to four years old and remain bonded for life.
The first nesting usually occurs when they are 4 or 5 years old.
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