The Mute Swan (Cygnus olor) is a species of swan, and thus a member of the waterfowl family Anatidae. It is native to much of Europe and Asia, and (as a rare winter visitor) the far north of Africa. It is also an introduced species in North America,Australasia and southern Africa. The name ‘mute’ derives from it being less vocal than other swan species. Measuring 125 to 170 cm (49 to 67 in) in length, this large swan is wholly white in plumage with an orange bill bordered with black. It is recognisable by its pronounced knob atop the bill.
The Mute Swan was first formally described 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. It is the type species of the genus Cygnus. Both cygnus and olor mean “swan” in Latin; cygnus is related to the Greek kyknos.
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. The species is monotypic with no living subspecies.
Mute Swan subfossils, 6,000 years old, have been found in post-glacial peat beds of East Anglia, Great Britain. They have also been recorded from Ireland east to Portugal and Italy, and from France, 13,000 BP (Desbrosse and Mourer-Chauvire 1972–1973).[full citation needed] The paleosubspecies Cygnus olor bergmanni, which differed only in size from the living bird, is known from fossils found in Azerbaijan.
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 national 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 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 Mute Swan is one of the heaviest flying birds, with males (known as cobs) averaging about 11–12 kg (24–26 lb) and the slightly smaller females (known as pens) weighing about 8.5–9 kg (19–20 lb).While the top normal weight for a big cob is 15 kg (33 lb), one unusually big Polish cob weighed almost 23 kg (51 lb) and this counts as the largest verified weight for a flying bird, although it has been questioned whether this heavyweight could still take flight.
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. All Mute Swans are white at maturity, though the feathers (particularly on the head and neck) are often stained orange-brown by iron and tannins in the water.
The morph immutabilis (“Polish Swan”) has pinkish (not dark grey) legs and dull white cygnets; as with white domestic geese, it is only found in populations with a history of domestication.