Mute swan

The mute swan (Cygnus olor) is a species of swan and a member of the waterfowl family Anatidae. It is native to much of Eurasia and (as a rare winter visitor) the far north of Africa. It is an introduced species in North America, home to the largest populations outside of its native range, with additional smaller introductions in Australasia and Southern Africa. The name "mute" derives from it being less vocal than other swan species. Measuring 125 to 160 cm (49 to 63 in) in length, this large swan is wholly white in plumage, with an orange beak bordered with black. It is recognisable by its pronounced knob atop the beak, which is larger in males.

The mute swan was first formally named by the German naturalist Johann Friedrich Gmelin as Anas olor in 1789 and was transferred by Johann Matthäus Bechstein to the new genus Cygnus in 1803. Both cygnus and olor mean "swan" in Latin; cygnus is a variant form of cycnus, borrowing from Greek κύκνος kyknos, a word of the same meaning.

Despite its Eurasian origin, its closest relatives are the black swan of Australia and the black-necked swan of South America, not the other Northern Hemisphere swans of the genus Cygnus. The species is monotypic, with no living subspecies.

Mute swan subfossils, dating back 6,000 years, have been found in post-glacial peat beds of East Anglia, Great Britain. They have been recorded from Ireland east to Portugal and Italy, and from France, 13,000 BP (Desbrosse and Mourer-Chauvire 1972–1973). Cygnus olor bergmanni, a paleosub species that differed only in size from the living bird, is known from fossils found in Azerbaijan. A related paleospecies recorded from fossils and subfossils is the Giant swan, Cygnus falconeri, a flightless species that lived on the islands of Malta and Sicily during the Middle Pleistocene.

Fossils of swan ancestors more distantly allied to the mute swan have been found in four U.S. states: California, Arizona, Idaho, and Oregon. The timeline runs from the Miocene to the late Pleistocene or 10,000 BP. The latest find was in Anza-Borrego Desert, a state park in California. Fossils from the Pleistocene include Cygnus paloregonus from Fossil Lake, Oregon, Froman's Ferry, Idaho, and Arizona, referred to by Howard in The Waterfowl of the World as "probably the mute type swan".

Adults of this large swan typically range from 140 to 160 cm (55 to 63 in) long, although they can range in extreme cases from 125 to 170 cm (49 to 67 in), with a 200 to 240 cm (79 to 94 in) wingspan. Males are larger than females and have a larger knob on their bill. On average, this is the second largest waterfowl species after the trumpeter swan, although male mute swans can easily match or even exceed a male trumpeter in mass. Among standard measurements of the mute swan, the wing chord measures 53–62.3 cm (20.9–24.5 in), the tarsus is 10–11.8 cm (3.9–4.6 in), and the bill is 6.9–9 cm (2.7–3.5 in). The plumage is white, while the legs are dark grey. The beak of the mute swan is bright orange, with black around the nostrils and a black nail.

The mute swan is one of the heaviest extant flying birds. In several studies from Great Britain, males (known as cobs) were found to average from about 10.6 to 11.87 kg (23.4 to 26.2 lb), with a weight range of 9.2–14.3 kg (20–32 lb), while the slightly smaller females (known as pens) averaged about 8.5 to 9.67 kg (18.7 to 21.3 lb), with a weight range of 7.6–10.6 kg (17–23 lb). While the top normal weight for a big cob is roughly 15 kg (33 lb), one unusually big Polish cob weighed almost 23 kg (51 lb), and this counts as the largest weight ever verified for a flying bird, although it has been questioned whether this heavyweight could still take flight. Mute swans can achieve speeds in flight of up to 88.5 km/h (55 mph), and during takeoff they achieve speeds of around 48 km/h (30 mph) when running to gain lift.

Young birds, called cygnets, are not the bright white of mature adults, and their bill is dull greyish-black, not orange, for the first year. The down may range from pure white to grey to buff, with grey/buff the most common. The white cygnets have a leucistic gene. Cygnets grow quickly, reaching a size close to their adult size in approximately three months after hatching. Cygnets typically retain their grey feathers until they are at least one year old, with the down on their wings having been replaced by flight feathers earlier that year.