Six swans including three cygnets are feared to have been stabbed and beheaded after their mutilated bodies were discovered in south London parks.
Patrols including local volunteers have been set up after the "grisly finds" in Thamesmead in the last month.
Two mute swans were found beheaded in Birchmere Park in November and another swan was also killed in Southmere Lake, the RSPCA said, as it launched an investigation.
Inspector Nick Wheelhouse said: "Park wardens have informed me that they're aware of the deaths of three swans, three cygnets and one Canada Goose so far in recent weeks.
"It's really concerning because the birds seem to have been stabbed and then beheaded, with their bodies left beside the water.
"While it's a serious animal welfare concern, it's also really upsetting for any of the park users who make the grisly find."
All wild mute swans in Britain are considered to be the property of the Crown and it is an offence to kill one.
Swans have statutory protection under the Wildlife and Countryside Act 1981 and anyone found guilty of trying to injure a wild bird, or kill or take it without a licence, can face up to six months in prison and/or a fine of up to £5,000.
Mr Wheelhouse said: "Neighbourhood wardens are now patrolling the area. And locals are so concerned about the birds that they've set up a patrol group to protect them, with various volunteers patrolling the area at night."
PA
