Traditionally, the British Monarch retains the right to ownership of all unmarked mute swans in open water, but only exercises ownership on certain stretches of the River Thames and its surrounding tributaries. This dates from the 12th century, during which time swans were a common food source for royalty. Swan Upping is a means of establishing a swan census and today also serves to check the health of swans. Under a Royal Charter of the 15th century, the Vintners' Company and the Dyers' Company, two Livery Companies of the City of London, are entitled to share in the Sovereign's ownership. They conduct the census through a process of ringing the swan's feet, but the swans are no longer eaten.
Swan Upping occurs annually during the third week of July. During the ceremony, the Queen's, the Vintners', and the Dyers' Swan Uppers row up the river in skiffs. Swans caught by the Queen's Swan Uppers under the direction of the Swan Marker are unmarked, except for a ring linked to the database of the British Trust for Ornithology (BTO). Those caught by the Dyers' and Vintners are identified as theirs by means of a further ring on the other leg. Today, only swans with cygnets are caught and ringed. This gives a yearly snapshot as to how well Thames swans are breeding. Originally, rather than being ringed, the swans would be marked on the bill, a practice reflected in the pub name The Swan with Two Necks, a corruption of "The Swan with Two Nicks".
On 20 July 2009, Queen Elizabeth II, as "Seigneur of the Swans," attended the Swan Upping ceremony for the first time in her reign, and the first time that a monarch has watched the ceremony in centuries.
A Queen's swan upper with a mute swan during 2010 swan upping at Henley-on-Thames
Swan Upping at Cookham, by Stanley Spencer, oil on canvas, 1915-19
- BBC News - Windsor Swan Upping ceremony cancelled due to flooding 
- Media related to Swan Upping at Wikimedia Commons
- The Royal Windsor website
- The official British Monarchy website - Swan Upping
- Swan Upping at Cookham