Windsor , England ( CNN ) -- The remains of a swan have been found barbecued near Queen Elizabeth II 's castle in Windsor , police said . By law , all unmarked mute swans in England and Wales belong to the queen . The swan had been killed and burned over the weekend , Thames Valley Police said . Its remains were found Sunday by a local council officer , who contacted police . The incident is being investigated as a theft , a police statement said . Anyone with information is urged to get in touch . Wendy Hermon , of the charity Swan Lifeline , told CNN of her disgust and puzzlement at the crime . `` It 's an act of vandalism which should n't happen , '' she said . `` The most sickening thing about all this is the swans will go to people because they think they are going to feed them . ... I always say they are semidomestic because they trust us , so it 's going into a trap . '' The majestic white birds are a fairly common sight on the River Thames , which flows past Windsor and on to London . According to the official website of the British monarchy , all mute swans have belonged to the Crown since the 12th century , when they were regarded as a delicacy and eaten at banquets . `` 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 Thames and its surrounding tributaries , '' it says . Each year , a census is carried out of the swans on stretches of the Thames in the counties of Middlesex , Surrey , Buckinghamshire , Berkshire and Oxfordshire , it says . This practice is known as swan upping . CNN 's Saskya Vandoorne reported from Windsor , and Laura Smith-Spark wrote in London .
Police say a swan was found killed and burned over the weekend . All mute swans in England and Wales belong to Queen Elizabeth II . `` It 's an act of vandalism which should n't happen , '' says swan charity worker .