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Penguin parents take off for feed

Taking a break Little penguins have developed a strategy to help them survive parenthood: take regular breaks away from the kids.

That's the finding of a study of Australian little penguins, commonly called 'fairy penguins', which has found that long trips away from the nest help penguin parents recover from the demands of feeding a ravenous brood.

The joint Australian and French study led by PhD candidate Claire Saraux from the University of Strasbourg challenges previously held beliefs that inshore birds, which forage short distances from land, only take long trips away from the nest when conditions are bad.

The research found that after the first couple of weeks of chick-raising, little penguins (Eudyptula minor) alternate between two consecutive long trips, followed by several short daily trips.

This strategy is well known in offshore seabirds but virtually unknown in inshore birds the researchers report in their study, which is in press in the journal Ecology.

The alternating long-short trip pattern is repeated regardless of food availability, says Dr Andre Chiaradia study co-author and penguin biologist with Phillip Island Nature Parks, where the penguin colony is based.

"We found that even in a good or a bad season … they have this long trip strategy. They [take multiple short trips to] feed the chicks … then they go for a long trip to get feed for themselves," Chiaradia says.

Penguin tagging

The findings were based on continuous monitoring of 200 little penguins from the Phillip Island colony over eight years.

During egg incubation and the first two to three weeks of a chick's life, parent penguins take turns guarding the nest until the other parent returns.

After a couple of weeks, in the 'post guard period' both birds head out to sea to hunt and neither may return for up to 14 days, during which time the chicks starve.

To understand what happens during this breeding phase, the researchers monitored the microchipped penguins as they passed over weigh-in platforms embedded into their natural pathways on the way to and from their feeding trips.

While short trips yielded more food for the chicks, the long trips enabled the parents to regain weight so that they could continue the gruelling short trip feeding cycle.

The researchers believe this pattern is triggered by a loss in body mass.

"During short trips [penguin parents] are not feeding for themselves, if they are they're little because they have this amazing thing where they can change the pH of their stomach to slow down digestion," explains Chiaradia.

"So then they bring this food in and give to the chicks, but over time they start to lose body condition because they're not eating properly so at some stage they say 'okay, that's enough, I have to look after myself before I actually die'."

"So then they go for long trips … and feed for themselves. When they come back … they bring food for the chicks but much, much less than they would do in a day trip because they are actually digesting that food for themselves."

Chiaradia says the strategy balances the demands of raising chicks and parental survival.

"When you raise your offspring, you put in a lot of effort, but you need to take some time to look after yourself before you burn out."

Reducing threats

Dr Belinda Cannell from the Centre for Fish and Fisheries Research at Murdoch University studies little penguins in Western Australia.

Cannell, who was not involved in the current study, has previously tracked penguins in the incubation and guard phases.

She says the Phillip Island study has important ramifications for how we manage the breeding areas of penguins.

"I certainly knew that they could travel long distances during incubation, but these long and short term foraging trips during the post-guard phase mean that they could be potentially accessing areas that they are accessing during incubation as well," says Cannell.

"It means that we've got to manage potentially larger areas than what we thought were critical for the birds while they are raising their chicks … so there's a much greater need for reducing threats whether it's threats to their food abundance or threats from water craft injury or any other coastal development threats."

Cannell says she would like to see comparative studies between different colonies that have different resources and environmental conditions to see if the long-short trip pattern is replicated.

"It would be interesting to see whether those longer foraging trips are further afield or if they're just more days close by."