Locals in New Zealand have gathered some 183 penguins they had found at the Ninety Mile Beach last week for later investigation in what appears to be the latest development in a phenomenon of dead penguins washing up on the island nation's beaches in vast numbers.

The kororā, a species of penguin characterized by its glossy blue color and known by the locals as little blue penguins, is the smallest species of the penguin family in the world, and they are native to New Zealand, but their population in the country is diminishing. The Department of Conservation classes the kororā as "at-risk" and "declining".

The wave of deaths has shocked locals as, over the past few months, hundreds have washed up on the shore and were found decaying on the Ninety Mile Beach and the Cable Bay.

Local residents have photographed a dead flock of 109 penguins at Ninety Mile Beach at the end of May in addition to the 183 dead found the same week as more than 100 were found at the Cable Bay. A resident found 40 dead at Tokerau Beach in the Northland region in mid-May, while the DoC received reports that at least 20 had died on the same beach at the start of the month.

There are many theories surrounding the events of mass deaths, with locals pondering whether they had been caught and dumped by fishermen, died due to the quality of the waters, or caught a fatal disease, such as avian malaria.

A DoC principal science advisor specializing in the field of sea birds, Graham Taylor, believes that more than 500 penguins have washed ashore since the start of May, projecting that the figure could be nearing 1,000. He also noted that it was difficult to give an accurate death toll, mainly due to the locals finding and burying many of them.

Despite the theories, scientists from the Ministry of Primary Studies who tested the bodies for diseases in a bid to find the reason behind their deaths concluded that the kororā had starved to death.

All of the bodies found on the sandy beaches of New Zealand were found extremely underweight, weighing less than their average size of 800-1000 grams.

"There was just no body fat on them. There was hardly any muscle to show. When they get to that stage of emaciation, they can't dive," Taylor said, noting that they would die of starvation or hypothermia due to the lack of blubber that keeps them warm.

However, Wellington underlined that the kororā were not starving due to overfishing. Instead, the main reason behind them not finding enough nutrients is the food chain disruption created by climate change, which is creating waters too hot for the fish they feed on.

The hottest ocean temperatures in recorded history were set last year, making for the sixth consecutive year that this record had been broken, as the fish that the kororā feeds on either go deeper in search of cooler waters or leave the area entirely because of the insufferable living conditions.

"This little species [of penguin] can dive down to 20 or 30 meters routinely, but it’s not that good at diving a lot deeper than that," Taylor says, as quoted by The Guardian. Hot water temperatures through winter had likely kept the fish out of reach.

It is not uncommon for mass deaths of sea birds to occur, as severe storms, heatwaves, or weather events can result in birds washing ashore in high numbers, but the frequency of the deaths is uncommon. 

Previously, deaths in these numbers would occur maybe once a decade. Over the past decade, Taylor said there have been at least three years where mass deaths were recorded, and this frequency is on an increase.