This is the biggest die-off for sooty shearwaters in northern New Zealand since the shearwater ‘wreck’ in 1999, which followed a large El Niño event in 1997-98.

DOC received reports about unusually high numbers of dead seabirds on North Island west coast beaches throughout November and early December.

“Starvation was confirmed as the cause of the bird deaths, not Highly Pathogenic Avian Influenza H5N1 (HPAI), which was the initial concern, and we suspect the starvation is related to climate change-induced ocean warming,” DOC Principal Science Advisor Graeme Taylor says.

“Our initial assessment is that the deaths are probably associated with unusually warm seas off the coast of Japan affecting the birds’ food stocks. In the spring migration, juvenile birds are returning from the coast off Japan to New Zealand in poor condition and dying when they get here.”

Sooty shearwaters, considered an at-risk species, were the most affected, followed by Buller’s shearwaters and fairy prions. All three species are dependent on conservation management measures to prevent further declines.

Principal Science Advisor Graeme Taylor says past tracking of sooty shearwaters revealed 70% of the New Zealand population migrates to seas north and east of Japan.

“A tagged bird we recaptured in 2024 showed an interesting change in route, departing New Zealand in May heading towards Japan then changing tack and heading east to the Gulf of Alaska.

“We presume the change resulted from unfavourable sea conditions off the coast of Japan.”

Graeme says the spring migration is now almost over, so reports of dead birds are expected to decline over the next month as the birds disappear from our beaches.

“However, we’re likely to see a higher frequency of seabird die-offs like this as oceans continue to get warmer and there’s less available food in their northern hemisphere foraging grounds”.

Graeme cautions people to be careful around any dead birds on the beach.

“HPAI has decimated seabird populations around the globe, and there are concerns it will get here eventually through infected migrant seabirds or marine mammals. It’s important to be careful.

“We normally ask people to weigh freshly dead birds, and we’d confirm if they’d died from starvation. However, due to the risk of HPAI, don’t touch, handle, or collect dead or sick birds to avoid spread of the virus and protect yourself.”

Members of the public should report groups of three or more sick or dead birds, marine mammals, or other wildlife to the MPI exotic pest and disease hotline: 0800 80 99 66.

In the meantime, DOC will continue to keep an eye on the situation and work with the Ministry for Primary Industries on monitoring dead seabirds around our coastlines.