UPDATED 5:28pm: Those heading to Waikato's beaches are being warned not to be alarmed if they spot large numbers of bird carcasses.
184 short-tailed shearwater have so far washed up between Waikorea Beach and Taharoa.
Department of Conservation principal science advisor Hugh Robertson says the deaths were probably caused by stormy weather, but admits it's a lot of birds in one go.
"On average probably between one and three hundred birds a year of that species, the short-tailed shearwater, would get wrecked on New Zealand beaches throughout the whole of New Zealand."
Rough weather is likely to be behind the birds washing up on Waikato beaches.
Mr Robertson says it's an unusually large number, but still a natural phenomenon.
"They're out there battling the winds and trying to get a feed at the same time out of the ocean.
"So if it's really rough weather, then it makes feeding a lot more difficult."