A rockhopper penguin on Campbell Island. Credit: David Thompson
Call it a happy feat.
New Zealand scientists have been astounded to find that two species of
subantarctuic penguin were able to travel 15,000km - equivalent to the
distance between Auckland and Boston - over a stretch of just six
months.
The insight was revealed by a tagging project observing nearly 100
subantarctic rockhopper and Snares penguins over winter in the Southern
Ocean.
"If they are constantly moving this averages out at about 100km a day
but you also have to add on to that the distances covered vertically as
the birds dive to capture food," said the study's leader, National
Institute of Water and Atmosphere seabird ecologist Dr David Thompson.
While the Snares penguin population on their craggy namesake islands was
relatively stable, Campbell Island's rockhoppers had dwindled by at
least 21 per cent since 1984, leaving just over 33,000 breeding pairs
there.
Rockhopper penguins on Campbell Island. Photo: Kyle Morrison
The island was once the world's largest breeding colony of the colourful
rockhoppers - the smallest of all penguin species and featured on the
movies Happy Feet and Surf's Up - but between 1942 and 1984 the
population dropped by about 94 per cent.
Researchers have been trying to understand what has caused the sharp decline, with big changes in their diet a suspected cause.
Thompson said the penguins' led an extreme lifestyle, taking them out into the ocean for long periods of time.
"They come to land to breed and when they finish that, go back out to sea where they feed up for a month," he said.
"Then they come back to land to sit and moult their feathers. During that period they don't eat at all."
Having virtually starved themselves, they then headed back out to sea in poor condition.
"They've grown a whole new set of feathers so their plumage is fantastic but it's quite demanding so they're really scrawny.
"We think winter is pretty important and that there is almost certainly
something going on in the ocean causing the population to decline."
The tags attached to the birds had to be modified from fitting the long,
skinny leg of an albatross to the short, stubby leg of a penguin.
Thompson and his colleagues also had to time their arrival on Campbell
Island, 620km south of Stewart Island, with the end of the moulting
season, just as the penguins were ready to leave for the winter.
Then they had to clamber down rock faces and steep cliffs to reach them.
Of the 90 penguins tagged for the project, about 80 returned the
following spring when the tags were retrieved and data processing began.
Tracking their movements was an eye-opening exercise.
The Snares penguin headed exclusively west towards Australia, while the
rockhoppers went east and covered a wider section of the ocean.
Several birds covered more than 15,000km over the winter.
The tags were also able to determine when the penguins were stationary, indicating they had stopped to dive for food or rest.
Thompson said this first tracking project had provided just a snapshot, but the work had to be start somewhere.
He plans to repeat the project and include other species, such as the erect crested penguin of the Antipodes Islands.
"The extra species will give us more information on how they relate to
each other when they go away. It may be that they use different space,
or it may be that populations of different islands get together at sea.
"Research like this is important to better understand what's important
for penguins. It is possible that particular parts of the ocean may help
them get through from one year to the next so we need to be able to
identify those places."
"Prior to this study we didn't have a clue where rockhoppers went in the
winter but the spaces they use in the ocean might be really important -
not only for them but for scientists to better understand what is
causing the population decline."
Credit: Murdoch University New research by Murdoch University will investigate the future of Rockingham's beloved Little Penguins colony.
Dr Belinda Cannell, who has been part of a long-term study of the birds, will spend the next three years examining their resilience to coastal waters that have remained warmer than average since late 2010 .
"Little Penguins are essentially the canaries in the coal mine for the Shoalwater Marine Park," she said.
"Understanding the viability of this population of penguins will give us a good understanding of the health of the whole ecosystem."
Dr Cannell will use new information collected over the next three years, along with data she has previously collected, to improve the understanding of how Little Penguins will fare with climate change and coastal development in the Shoalwater Islands Marine Park.
She will continue to track Little Penguins at sea using satellite and GPS technology, attaching special tags to some birds to record the diving depths when travelling and foraging.
"For the first time we will gain a real understanding of the movements and activities of the penguins in the water and show locations where they may be more at risk from watercraft collisions," she said.
Dr Cannell is also hoping to calculate the size of the penguin population and exactly what the penguins are eating.
"We have not done a full population count of the penguins since 2012 but other indicators have not been promising," she said.
"From 2010 to 2015 far fewer penguins were recorded using nest boxes and, not surprisingly, fewer eggs were laid. We believe this was connected to water temperatures being higher than average.
"The birds have been travelling long distances when they are relieved of incubating the eggs, some travelling down to Geographe Bay. Their foraging trips have been incredibly long, 10 days or more. This indicates food resources close to Penguin Island have been scarce."
Dr Cannell said water temperatures were still warmer than normal in summer this year, but have now dropped back to normal. She is hoping to see a shift in the penguins' behaviour, indicating the coastal waters near Penguin Island are again supporting healthy baitfish stocks.
