The SPCA hasn't been able to find the person responsible and is treating it as an ongoing investigation.
The reports are of a variety on non-native birds decorated in tinsel and other decorations including gold and red tinsel bows, pink and blue ribbons and yellow feathers.
"We don't yet know if this is an act of intentional cruelty, but the birds are suffering so we're speaking out in the hopes that it stops," SPCA Wellington said.
"After extensive efforts by our Inspectorate Team we were unable to find the person responsible. We are continuing to treat this as an ongoing investigation."