The bird was brought into Allambie Vet Clinic last month after it was found walking around a backyard.
The bird was originally thought to have a wing injury and was unable to fly.
The bird was rehomed, but later taken to Northern Districts Veterinary Hospital which found metal pellets in the bird's shoulder, believed from a BB gun.
Northern Districts head nurse Lisa Milham said the bird was unable to fly because the shots had fractured its shoulder.
The bird, which Miss Milham believed was wild, had to be put down because of the pain it was in.
"The fact they think it's funny to practise their shooting on wildlife, I think it's disgusting," she said.
Allambie clinic owner and senior vet Brian Mills believed the animal was someone's pet, which had been shot after it escaped.
"I think it's a disgrace. I don't think people should be allowed to have weapons," he said.
"If it was someone's pet, it's got out and someone shot it. It's really lousy."
Mr Mills and Miss Milham said it was not uncommon for shot animals to be brought in. Anyone who has found an animal injured in this way should contact their nearest vet and police.
WHAT TO DO
If you find an animal that you think has been shot:
* Take the animal to your nearest vet.
* If the animal is native, contact Wildlife Information, Rescue and Education Service (WIRES) or Sydney Metropolitan Wildlife Service.
* Take note of where the animal was found and when.
* Contact police or ensure the vet does so.
WIRES: 1300 094 737.
Sydney Metropolitan Wildlife Service: 9413 4300.