Satellite tracking has revealed that tawaki, or Fiordland crested penguins, travel “tremendous distances,” says penguin researcher Thomas Mattern.
Twice a year their record-breaking travels take them from temperate New Zealand down into subantarctic waters, and Thomas says the only explanation that makes sense is that they have an ancestral memory of having once been a subantarctic species.
Previous research on breeding tawaki shows that they feed close to where their nests are. Many birds breeding in Milford Sound, for example, stay within the fiord or travel just outside.
But once breeding is complete, these stay-at-homes turn into nomadic ocean swimmers, embarking on a marathon that lasts about two months until they must return to land to moult.
“They practically run a marathon when their main goal is to gain weight.”
Some tagged birds covered about a thousand kilometres per week and covered up to 7500 kilometres in total. Thomas says they swam fast and far, as they had a limited time frame before they needed to return to land.
“They travel to the heart of the subantarctic, halfway to Antarctica at least,” says Thomas, from the Tawaki Project and the University of Otago.
“It’s the longest distance that any penguin we know covers at that stage of their life history.”
The penguins swam to an area at about 60° south, just north of the Antarctic convergence where cold polar waters meet warmer temperate waters.
The birds are undoubtedly finding good food supplies to enable them to regain weight lost during breeding and put on more weight ahead of the moult, but Thomas says that in terms of ocean productivity and food supply, temperate waters around New Zealand are more productive at that time of year, so food alone isn’t the reason the birds go so far.
He says that although tawaki are a temperate species, all other crested penguins live and breed in the subantarctic, “so it is really a return to their ancestral home.”
“We think that it’s just hard-wired in their brain to go down to the subantarctic region because that’s where they come from.”
During the moult, penguins remain ashore for three to four weeks. They replace every feather – about 150,000 feathers in total – and don’t feed as they have lost their usual waterproofing and aren’t able to swim.
Tawaki return to sea after the moult to put on weight ready for the next breeding season, and once again satellite tracking is revealing where the birds go.
Thomas says he was surprised to find that the birds are essentially making the same journey to the subantarctic polar front, albeit swimming more slowly as they have more time.
This project is still underway, and the tawaki are still swimming.
Flint's coming home! After two months at sea, covering a distance of more than 6,500 km, and reaching the Polar Front on his journey, the penguin is only 800 km from its home on Whenua Hou. At this pace he'll be home in 3 weeks time. #MarathonPenguin pic.twitter.com/0BImoGH7Wp— Tawaki Project (@TawakiProject) May 25, 2019
Thomas and colleagues have published the results of the pre-moult tracking study in a free access paper called ‘Marathon penguins – Reasons and consequences of long-range dispersal in Fiordland penguins / Tawaki during the pre-moult period.’