Four native gulls have died in Whangārei at the weekend after they were found covered in an unknown substance.
Whangārei Native Bird Recovery Centre manager Robert Webb said he was bracing for additional arrivals on Monday as more have been sighted across the district covered in what he believes may be diesel oil.
Northland Regional Council [NRC] has appealed to the public to check around their properties and garages for the possible source following the death of the red-billed gulls, which are a protected species.
Compliance monitoring manager general for NRC Cathy Orevich said the source was not believed to be a large oil spill as this would likely have been reported to the council.
It could be something like a domestic drum filled with the substance, she said.