Dozens of birds in New Zealand were found dead or injured with Christmas decorations tied around them, arousing calls for anyone with information about the author of the cruel attacks manifesting themselves.

New Zealand Royal Society for the Prevention of Cruelty to Victims Animals (SPCA) said that a number of sparrows and pigeons had been linked to "decorative trinkets" in the capital, Wellington.

Some animals are starving, unable to fly and find food, the SPCA said. The charity noted that while there have been similar incidents in the past, there has been an increase in sightings in recent weeks.

"Those who survive and arrive at our center are still in a very bad state and are so malnourished and afflicted that we had to euthanize them humanely," SPCA spokeswoman Paige Janssen told the BBC.

Janssen said that several "decorated" bird cases had been reported since 2015, but that the number of sightings had increased between Christmas and the New Year.

"We received about 30 calls for this period. There have been many sightings from a dozen still-flying birds flying around the Kilbirnie area that we can not reach, "she said.

On Wednesday, a property was searched for the purpose of finding the so-called Wellington Sparrow Killer and the local SPCA said that she was looking for the suspect behind this "case of cruelty". Last week, he launched a call for information.

The Central Regional Director of the SPCA, Ros Alsford, told the New Zealand Herald the decorated pigeons were removed from the property on Wednesday and taken to the hospital where they received a check and the trinkets were removed.

She said the birds were incredibly distressed when they arrived, but they were fine now. "They were in good health, the vets gave them a good health check. And once we removed the trinkets, we returned them to the property … The reason we did it is that they were sitting on egg nests, so we had to bring them back to their nest. "