For the second year in a row shearwater birds have also arrived late at Port Fairy's Griffiths Island with observers unsure why.

While normally arriving at Middle Island in October, about 15 penguins had turned up early last July to breed but were killed by foxes or dogs.

However, the total population of the colony was estimated at 70 to 100 penguins, according to the project season report which was recently presented to the city council but none of them bred.

The report on the "disappointing season" says the colony lost half its male breeders in the July attack.

Warrnambool Coastal Landcare Network penguin volunteer coordinator Dr Trish Corbett said they could only guess when the penguins would arrive this year.

"We have no idea what's going on as last year they didn't arrive until December," she said.

"There were a couple of pairs who could've bred but didn't and we can only assume they didn't as it was too late in the season.

"In February to sometime in the start of March each penguin gets forced into moulting. If they had started breeding in December there wouldn't be time to feed and then burrow for three weeks to moult."

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Dr Corbett said a heatwave in Antarctica caused the Bonney Upwelling off the coast of Portland to run a month late. This delayed the arrival of penguins to Middle Island in 2019 as the Bonney Upwelling provides food for marine life.

"It seems like the Bonney Upwelling is what was driving the penguins," she said.

"I did hear that the short-tailed shearwaters were late again this year and they were late last year.

"That could give us some indication about the penguins.

"There's definitely different things happening but we don't know what to expect."

Dr Corbett said the Maremma guard dogs were well prepared for the upcoming season.

"We've got a few Maremmas who are our guardians at the moment; Mezzo and Isola," she said. "Mezzo is our lead guardian and Isola is our back up.

"We also have Oberon who is a bit over 12 months. He is still in training but showing amazing signs of being a good guardian.

"We retired Tula last year and Eudy is still our back up but this will be her last season."

The Meet the Maremma program was cut short due to the coronavirus pandemic in March but ticket sales made a total income of $15,652 in the 2019/20 financial year.

Signs of the short-tailed shearwaters' arrival was confirmed on October 4 after burrows were cleaned in preparation for the nesting season on Griffiths Island.

Friends of Griffiths Island chair Marten Syme said it was the second consecutive year the shearwaters had arrived later than their expected September 22.

"It's never been formally determined why they were late last year but they were late arriving throughout Australia, not just in Port Fairy," he said.

"Their extended delay indicated something was chronically wrong and there were various suggestions, whether it could have been the Fukushima problem in Japan, shortage of fish or weather conditions from climate change.

"The predominate issue appears to be food stock on the way or they haven't built up food reserves in the northern hemisphere."

From his observations last year, Mr Syme said the short-tailed shearwater numbers were "noticeably down".

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He said the shearwaters might have postponed their journey until they had a sufficient amount of food to equip them for their long journey from Japan.

He said if the birds came to Port Fairy undernourished, it could be a reason behind onshore deaths.

"At the most southern location of burrows in Griffith Island there was substantial mortality last year," he said.

"What I do think is when the birds come out of their burrows the next morning to fish after their journey, if they don't get off the ground quick enough, they drop back exhausted and the ravens attack."

The short-tailed shearwaters boast a colony of around 40,000 and leave Griffith Island around the middle of April and the young, in early May.

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