Residents have called for action after seeing geese being shot and barbecued on Mitcham Common.
The claims emerged after a group set a large campfire on Saturday, August 11, at Seven Islands Pond, after which a passerby said he found what he believed to be the charred remains of a Canada goose wing.
One resident, who regularly walks her dog on the common but did not wish to be named, said three men were seen gutting a goose in the bushes while another said they had seen men using a catapult to shoot at geese on the pond.
She said: "It’s terrible. If I saw anything doing that I would have phoned the police straight away.
"I wouldn’t care who they were, I would have gone berserk but I think people are frightened."
Lighting any kind of fire on the common is strictly against Mitcham Common's 1981 byelaws.
The same woman had previously complained to Merton police about a group of men persistently gathering to drink on Mitcham Common after they threw a bottle at her.
She said: "I have been concerned for a couple of months now about the number of people that have been over the Seven Islands pond on Mitcham Common - Eastern Europeans of all different types -
Polish, Russian and Ukrainian.
"I was walking past where they were drinking and they made some comment.
"I ignored them but they shouted out - and then they through a bottle and it crashed behind me."
Melanie Nunzet, who runs her own Mitcham common walks, said: "People think it is their common.
"They think nobody is looking at them and that they can do what they like.
"I think it has happened with fish as well - it's appalling.
"There’s not a single goose out there now because they are frightened and they must have gone elsewhere."
Merton police said they were aware of a number of issues regarding Mitcham Common and have since increased patrols in the area.
A spokesman said: "Many of these issues have been passed to us third-hand, and have not been reported to police at the time they happened, which obviously this makes it very difficult for police to take any action."
Anyone who sees anti-social behaviour at any time should call Merton police on 0208 649 3604 or to the non-emergency number, 101.
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