Swan upping
Swan Upping is an annual ceremonial and practical activity in Britain in which mute swans on the River Thames are rounded up, caught, marked, and then released.
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. The Swan markers ring 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 remain unmarked, those caught by the Dyers' are ringed on one leg, and those caught by the Vintners are ringed on both legs.
On 20 July, 2009 H.M. 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.
(wikipwdia.org)