Wellington penguin colony loses 82 chicks this season to starvation
Thursday, 28 January 2021
Thirty-five per cent of little blue penguins born on the Matiu/Somes Island have died of starvation after an otherwise successful breeding season.
During a fortnightly survey of the colony in mid-November, the Wellington Harbour Penguin Study team discovered 66 dead chicks – 54 of them in one day.
The island, home to up to 800 little blues, is a haven for wildlife, but heavy rain flushing silt into the harbour and a shortage of food due to warmer waters means the penguin population has been hit hard.
Penguin specialist Mike Rumble said it was a devastating discovery for his team. “82 out of 236 chicks is a very large loss.”
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The team, 21 members-strong, had been surveying the island since 2004. Matiu/Somes is a predator-free island, and always showed strong growth. That was anywhere between 3 and 8 times more than a normal year.
By the end of nesting season – only one chick now remained to leave the nest for wider waters – the number of dead chicks had risen to 82.
After fledging, the chicks would be “out there somewhere for the next two years, and then they return – we hope”.
From a vantage point on the island, Rumble could see clear silt lines flowing south past the island on both sides, usually a strong indicator that rain was flushing silt from the Hutt River into the harbour from the north.
“Silt takes a long time to go, and once you've got silt, you contribute to the climate change-oriented issue of harbour temperature.
“We knew [the temperature] was up, and we know that it impacts strongly on the ability of parents to forage for food,” Rumble said.
“The fish stay down in the cold currents, so if the temperature is up, then you don't get these cold currents rising, making life very miserable for the parents.”
To make matters worse, any fish that did rise to warmer waters went unseen because of the silt.
And the penguin chicks back in the nests? “They starved.”
One penguin chick was sent away to Massey University in Palmerston North for a pathogen test, and they returned the same answer.
“Whatever caused it struck quickly,” Rumble said. “It’s a very large number of chicks lost in a very short time frame.”
The chicks were voracious eaters, so three to four days would have been enough for them to waste away.
The issue was short-lived, with the parents returning with food for the remaining chicks as the water cleared. But for these chicks, their growth rate was slow.
The survival rate was “very low for seabirds in their first year anyway”, Rumble said, and the team would likely not see results from this breeding season for two to three seasons, when the chicks returned as adults to nest.
The lower number of penguins would have a knock on effect; the species which fed on penguins would now have less to eat.
For Rumble, the penguins were the canary in the coal mine. If the situation was dire for the little blues, what was happening in the great beyond?