The RSPCA said: “One of our officers has already been out to try and catch the bird who is fully mobile and we’re told has been like this for some time.
“It’s sad to think that someone has targeted a wild animal in this cruel way and we understand what an upsetting sight it is for local people.
“We’d like to reassure the public that presently the duck is able to eat, swim, socialise and fly.
“The bird is also extremely wary and will fly away when anyone goes near, so attempting a boat rescue is also unlikely to result in a successful outcome.
“We’ve asked the person who kindly got in touch with us to continue monitoring and feeding the duck, which they are happy to do, and to contact us again if the bird is successfully caught.
“We are so grateful for their help and kindness,” the charity added.