Slow start to penguin breeding

A slower start to the little blue penguin breeding season at Oamaru Creek could be due to the disturbance of nesting boxes for the Oamaru Harbour foreshore protection work that is under way.

Philippa Agnew.
Philippa Agnew.

But the breeding season was not at risk for the birds outside the protected Oamaru Blue Penguin Colony, colony research scientist Dr Philippa Agnew said.

After a false start in May, there were now 17 eggs at the commercial colony at the old quarry, and across the harbour at the Oamaru Creek colony the first egg was laid just this week.

The foreshore protection work involved shifting the Oamaru Creek colony’s nearly 250 nesting boxes.

"It probably has something to do with the boxes being moved, because we’re noticing different birds in different boxes. It is probably taking them a wee bit of time to adjust to it, but they’ll be fine," Dr Agnew said.

At the end of May, two eggs were laid at the commercial colony - the earliest eggs laid at Oamaru Harbour since the late 1990s - but the nest failed; the chicks hatched a month later and then died in their first week.

With egg laying expected to peak in August, it was still too early to say whether this would be a successful breeding season for either colony.

‘‘It’s a start,’’ Dr Agnew said. "We’ll have upwards of 200 or 300 eggs laid [at the commercial colony]."

An unusual penguin behaviour had caught the attention of staff at Oamaru Blue Penguin Colony, Dr Agnew said.

Weekly monitoring this winter showed three-week cycles which peaked with large numbers of birds "staying home".

"They’re just in a cyclical pattern of all being ashore at once, and then all going out to sea at the same time, and then all coming in. It’s really strange."

During weekly monitoring at the colony on July 19, staff found 235 penguins at home in their boxes. The week before only nine had stayed ashore during the day during weekly monitoring.

June showed the same large fluctuations. Dr Agnew could not account for this winter’s extreme cycles.

Scientists generally believed penguins did not forage in social groups, but a recent study in Australia - and some anecdotal evidence - suggested the birds might.

But when ashore the birds were social - and that could "drive the numbers" that stay at home.

"If there are a lot that stay home, that might encourage other birds to stay at home," Dr Agnew said.

"They might just decide to stay because lots of other birds decided to stay, as well."

As the breeding season progressed and the number of eggs laid at the colony increased, more birds would be staying at home to be with the eggs.


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