Thousands of young muttonbirds have starved to death on Stewart Island and the Titi Islands this season because parental birds have abandoned their chicks in search of food.

Experts say warmer ocean temperatures have pushed small fish that the birds eat such as krill, squid and sardines into deeper and colder waters where they thrive. The muttonbirds have followed them to those colder waters.

Invercargill naturalist Lloyd Esler did an annual count of muttonbirds on Mason Bay, Stewart Island, at the weekend, which revealed the most dead muttonbirds he had seen in about 15 years.

Almost 2000 dead birds were found washed up on the shore compared with about 100 in previous years, he said.

There was a "glitch" in the food supply and it could be because warm currents moved small fish into water too deep for the birds to catch, Mr Esler said.

Kaumatua of Waihopai Runaka Michael Skerrett said muttonbirds were in terrible condition this season and the number of chicks were down.

It could be because of El Nino climatic conditions, he said.

Regular muttonbirder Jane Davis said the situation was probably as bad as it could be.

While there were good hatching numbers at the Titi Islands most ended up dying at the mouth of their nest because they were not being fed, she said.

Parental birds chose to look after themselves, some foraging for food halfway between New Zealand and Australia, and not returning to feed their young at night, she said.

"Usually at night the sky is full and the island just rocks with sound. This year you could almost count them and it was silent.

"When we realised what it was like we just bought enough back for the family, she said.

Meanwhile, warmer ocean temperatures has also taken its toll on other seabirds.

Poutiri ao o Tane manager, Ken Hunt, who planned to move 100 mottled petrel chicks from Codfish Island to Hawke's Bay as part of a six-year project, said the relocation had been postponed until next year.

Visiting the island last month, Mr Hunt said muttonbirds and mottled petrel were "literally starving" to death.

More than 200 chicks hatched but only 25 were of suitable weight and wing-span for relocation, he said.

There was not sufficient food and the time between parental feeding was longer, Mr Hunt said.

The muttonbirding season started in April and goes until the end of the month.