Friday, September 9, 2011

Little penguins think big when it comes to feeding

The penguins of Victoria's Phillip Island have been found to employ sophisticated feeding strategies while breeding.
PHILLIP ISLAND'S MUCH-LOVED little penguins have been found to use a sophisticated feeding strategy that allows them to remain in top condition whilst raising their chicks.
Little or 'fairy' penguins (Eudyptula minor), which are around 30cm tall as adults, are the smallest of the world's 17 penguin species. They are found in colonies on the southern coast of Australia - such as Phillip Island, near Melbourne, and also in Sydney's North Harbour - and all around the coast of New Zealand.
For a new study, detailed in an upcoming edition of the journal Ecology, data from hundreds of penguins were collected over eight years to hone in on feeding strategies of breeding pairs. A team of French and Australian scientists found that these penguins alternate between short and long feeding trips, balancing their own need for food with that of their chicks.

Australia only penguin

"When little penguins finish what we call the 'guard stage' and can first leave their chicks for extended periods of time, they are quite hungry, so they go on two long trips, which allows them to replenish their own energy stocks," says Dr Andre Chiaradia, a biologist at Phillip Island Nature Parks and co-author of the study.
"These extended journeys are well known in offshore seabirds like albatross, but normally we would expect inshore seabirds like the little penguin to take only short trips," he told Australian Geographic.
"Short foraging trips yield larger meals and allow for regular provisioning of chicks. But adults can deplete their energy reserves during these trips and ultimately risk their own survival," says co-author Claire Saraux, a PhD student from the University of Strasbourg in France.

To replenish themselves, adults have to take some longer trips when they reach a critically low body weight, she says. "The two consecutive long trips therefore enable little penguin parents to rebuild their reserves before another round of short trips."

Little penguins in a nest on Phillip Island, which is 140km south-east of Melbourne. (Credit: Daniel Cranton Photography).

New approach to study

While little penguins have been observed at Phillip Island for over 40 years, Andre says this study takes a new approach by closely examining the behaviour of  individual birds. "We have collected data over eight years using microchips, similar to those you might have in a pet, and also a weigh bridge with sensors, so we know exactly when an individual goes out to feed and how long it is gone for."
When they collated the data, Andre's team noticed the alternating lengths of feeding excursions. "It was clear that these birds would take more short trips to feed their chicks during good seasons, while during bad times they would do less of this," he says. "They always take regular long trips, however, no matter what food availability is like."
"While it is the first time this behaviour has been observed in an inshore species, it doesn't surprise me," comments Dr Thomas Mattern, an ecologist at the University of Otago in New Zealand. The adult penguins expend significant time and energy nurturing their chicks, so must also find time to feed themselves, he says. "If I had to eat baby food day-in, day-out... I would be very tempted myself to sneak away for a decent steak and beer every now and then too."


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