Nesting takahē and their chicks could be at risk if a possible cat sighting on two pest free islands in the Hauraki Gulf is confirmed.
On Tuesday, two members of the public reported separate sightings of a black cat on Motutapu and Rangitoto Islands, which are connected by a short bridge.
The Department of Conservation (DOC) sent two conservation dogs, their handler and other staff to the islands off Auckland early this morning.
There are about 18 threatened, nationally vulnerable takahē on Motutapu, as well as nationally critical shore plover, nationally vulnerable dotterels and at-risk brown kiwi.
DOC Auckland inner islands operations manager Keith Gell said 17 traps had been set in the Islington Bay area, near where the cat was sighted.
Mr Gell said evidence of something eating tui and kakariki in the area was found by DOC staff, but there was no evidence of predation on any of the threatened species yet.
"The endangered species that we are worried about are the shore plovers and the takahē chicks," he said.
New Zealand's current wild shore plover population is only about 240.
Mr Gell said the DOC team would skirt the Islington Bay area with the dogs, looking to confirm the existence of a cat on the island by scent, or by finding droppings.
He said the cat must have come ashore by boat. It was possibly a stow away, or may have been deliberately dumped.
"Someone's brought it on to the island for some reason - you just can't explain it."
He hoped the cat would be enticed into the baited trap - which would catch, rather than kill it.