Swan Upping takes place once a year on the River Thames.  The Swan Uppers weigh and measure the cygnets and check them for any signs of injury, commonly caused by fishing hooks and line.  The young cygnets are ringed with individual identification numbers that denote their ownership if they belong to the Vintners or the Dyers livery companies; the cygnets’ ownership is determined by their parentage. However, all Crown birds are left unmarked.  The Queen retains the right to claim ownership of any unmarked mute swan swimming in open waters, but this right is mainly exercised on certain stretches of the River Thames.

For more information visit: Royal swans