The rise in seawater temperatures could be to blame for hundreds of dead fairy prions washing up along the beaches in Tasman and Golden Bay.
There have been reports of people finding hundreds of dead, dehydrated and starving seabirds across the entire Tasman Bay, and all the way to Wharariki in Golden Bay.
Some are dropping the blue-grey birds to Natureland Wildlife Trust, in Nelson.
Director Meg Rutledge said they were currently caring for 13 dehydrated and starving birds, with more expected to arrive.
"It's not the first time historically that there have been such mass dying off of birds," she said.
"The cause can be things like bad weather, or high heat that has affected the movement of their food sources so they are going hungry."
She had been getting reports of the birds all around Tasman Bay getting into trouble on the shore break, and then washing up on the sand.
"There are many that have passed away. Some are dehydrated from lack of food, and some that are fit enough to make a full recovery."
They were working with Department of Conservation (DOC) to make sure the birds were getting the right treatment at Natureland.

Hundreds of seabirds have also been found sick or dying on Northland's east coast beaches earlier this month.
Dead and starving penguins have also been reported on Auckland's Waiheke Island and North Shore, the Coromandel Peninsula and Kaikōura.
The fairy prion is an abundant petrel of exposed coastal waters around New Zealand, especially from Cook Strait southwards.
It often feeds in large flocks over tide rips near offshore rocks and islands.
DOC senior communications advisor Herb Christophers said fairy prions are fledging at this time of year.
"If conditions at sea are unfavourable for them to find food, like the weather fluctuation ... then they will struggle."
Comment: The above story came from South Island, see also this recent report from North Island: Mass of dead and dying seabirds on Bay of Plenty shores in New Zealand