More needs to be done to protect critically endangered Codfish Island / Whenua Hou diving petrels, researchers say.
There are just 200 of the birds left at a single breeding colony in the dunes on Whenua Hou, near Rakiura / Stewart Island.
The birds - known as kuaka in Ngāi Tahu dialect - were once widely found in coastal dunes across southern New Zealand, but it wasn't until 2018 that it was discovered they were a distinct species of petrel.
However, invasive predators destroyed all breeding colonies except one.
Although Whenua Hou has been predator-free since 2000, other threats remain, including storms, climate change, and competition with common diving petrels.
The research by Victoria University of Wellington, the Department of Conservation and the University of California has been trying to piece together more information about the threats the little-known birds face.
Lead author Johannes Fischer, who recently completed his PhD on the birds, said until this study, the offshore threats affecting kuaka had not been studied.
Birds were tracked for three years, allowing researchers to identify offshore distribution, movement, behaviour, and overlap with vessels.
"These birds travel thousands of kilometres to their non-breeding grounds, where the birds then stop flying altogether and spend months on, or under, water, becoming basically tiny 'flying penguins'," Fischer said.
"At their non-breeding distribution, these birds appear safe from adverse interactions with marine users."
However, the birds' breeding grounds overlap with marine areas used by boats.
Fischer said light pollution may cause what was known as 'deck strikes' - when birds collide with vessels because they have been disoriented by artificial lights.
But Fischer said more study was needed in this area.
However, the researchers have made a number of recommendations to minimise deck strikes:
- alert marine users to the risks of spotlights and deck lighting
- use black-out blinds
- minimise external deck lighting
- provide protocols on treatment and release of deck-struck birds
- keep records of deck strikes (including photographs to aid identification of diving petrels)
Conversations with a number of organisations are already underway to find ways to better protect the species.