Mute swan  (Cygnus olor)

The mute swan is Britain's largest bird (3), and one of the heaviest flying birds in the world (4); adults can weigh over 15 kg (3). The combination of their large size, very long neck, white plumage and orange-red bill with a black knob towards the top of the bill makes them easily to recognise (2). Males (cobs) and females (pens) are similar in appearance, although males are slightly larger and have a more prominent knob on the bill (4). Juveniles are greyish-brown with a grey bill, which lacks the knob seen in adults (2). Contrary to the name, the mute swan produces a range of vocalisations, including a rumbling 'heeorr', and an aggressive hissing noise when threatened (2). The wings make a loud 'clanking' in flight (8).

Found throughout Britain, but absent from high ground and areas without fresh water (3). After 1960, the population began to decline as a result of poisoning from lead fishing weights (3). Since the mid-1980s and the banning of lead weights however, the population has increased (5). Outside of Britain, the mute swan is known throughout Europe and central Asia (6); it has also been introduced to New Zealand, Australia, South Africa, and North America (4).

Found in a wide range of water bodies, including rivers, lakes, ponds, reservoirs, flood waters, tidal estuaries, and sheltered coasts (4).

The mute swan feeds chiefly on submerged aquatic vegetation, which is obtained by upending (tipping head first into the water, so that the tail remains visible above the surface) (4). It also feeds in fields on young cereal crops (8), spilt grain (4), and on artificial food sources, such as bread given by the public (3).

Territorial disputes may result in aggressive fights between males, in which they rush at one another and slide along the surface of the water (2). Pairs typically nest solitarily, although semi-domesticated birds may nest in large colonies (6) (notably at Abbotsbury in Dorset) (8). The cone-shaped nest is built at the edge of the water, and may be used in subsequent years by the same pair (4). After mid-April, between 5 and 7 (up to 12) whitish or pale blue eggs are laid. They are incubated, mainly by the female, for 35-42 days; the young, known as 'cygnets', leave the nest soon after hatching (4). Both parents take care of the cygnets for an extended period, often until the next breeding season (4).

Harsh winters and poisoning from lead fishing weights were responsible for the decline of the mute swan population in Britain. A series of mild winters combined with the banning of lead weights has resulted in the recovery of the numbers of this beautiful bird (5).

Strong lobbying to ban lead fishing weights has enabled mute swans to recover from the crash in numbers caused by lead poisoning. They will also have benefited from action carried out for other species of wildfowl, such as the creation and management of wetland nature reserves (8).

For more on British birds, see the RSPB website:
http://www.rspb.org.uk
For more on this species see the RSPB's mute swan information:
http://www.rspb.org.uk/birds/muteswan/?page=m

Information authenticated by the RSPB:
http://www.rspb.org.uk/