The annual Swan Upping began today in London, England. The five-day census—which dates back to the twelfth century—counts swans and young cygnets belonging to the Queen, while watching for signs of injury or disease. According to Reuters, the ceremony began in the 1100s, when the Crown claimed ownership of all mute swans in the kingdom. “Today, the Crown retains the right to ownership of all unmarked mute swans in open water, but the Queen only exercises her ownership on certain stretches of the River Thames and its surrounding tributaries.” The Swan Upping takes place on the third week of July every year, and collected below are images of the event from recent years.