Swan upping is the traditional means by which the swans on the Thames are apportioned among the three proprietors. Its main practical purposes today are to conduct a
census of swans and check their health. It occurs annually in the third week of July. Over five days, the Crown's, the Vintners' and the Dyers' respective 'swan uppers' row up the river in
skiffs (in recent centuries from
Sunbury to
Abingdon). The Crown's swans are recorded by the
Marker of the Swans, who is rowed in a skiff by oarsmen from the
Company of Watermen and Lightermen. The Crown's swan uppers, who wear distinctive red uniforms, catch the swans, weigh and measure the
cygnets, and check them for injuries. Based on their parentage, cygnets are determined to belong to the Crown, the Dyers or the Vintners. Swans belonging to the Crown are left unmarked, except for a lightweight ring linked to the database of the
British Trust for Ornithology. Those belonging to the Dyers and Vintners receive a similar ring on the other leg. The rings have replaced nicks on the swans'
bills, which used to be made with a metal implement, one nick for the Dyers and one on each side for the Vintners. The former practice is reflected in
The Swan with Two Necks, the name of a former pub in the City connected with the Vintners, which was a corruption of "The Swan with Two Nicks". == Seigneur of the Swans ==