27 Jan, 2018 7:30am
Dead gulls found near Grovers Island, in the Clutha River near Roxburgh in Central Otago, will be tested to establish their cause of death.
Mykayla Robert, of Roxburgh, found the gulls while she was walking last weekend.
Posting on Facebook, Miss Robert commented that she was not sure how they died.
"I found at least 30-40 dead seagulls on that little island, mainly on the Clutha River side," Robert said.
Robert took pictures of the dead gulls.
"As you can see, there was one or two seagulls every metre right along the shore line," she said.
Department of Conservation (Doc) senior ranger, biodiversity, for Central Otago John Keene said a Doc ranger investigated the site that day and estimated up to 40 black-billed gulls were dead.
The ranger did not see any obvious signs on the carcasses of damage from animal predators, Mr Keene said.
The area was known for being a breeding colony site for black-billed gulls, an endangered species.
This was the second time mysterious deaths at the colony had been discovered, he said.