The Mysterious Case of the Missing Muttonbirds

Karen Hunt 30/1/20

A short-tailed shearwater corpse on Griffith Island, Warnambool.

Something is killing the shearwaters on Griffith Island at Warnambool.

The Island, on Victoria’s southwestern coast, is the home to one of the largest nesting colonies of Short-tailed Shearwaters (aka muttonbirds) on the mainland of Australia.

Or it usually is.

In January as I walked around the colony on Griffith Island, I was shocked to see the number of corpses littering the landscape, both adults and fluffy, unfledged chicks.

The last time I was on the Island, two years ago, the same walk produced not even one corpse, so to say I was shocked is an uderstatement.

And it appears this is not the only mystery surrounding the muttonbirds – at least half the population is missing. The migratory birds usually touch down at Griffith Island after their incredible flight from Alaska on September 22, but this year not only were they late, but there was only about half the usual number.

I contacted Peter Barrand, President of Birdlife Warnambool, the closest Birdlife group, to see if he had any answers

In the case of the missing muttonbirds, what he says is alarming, although given the lack of useful information about the migratory species, its all theory. Reports from the northern hemisphere, where the birds spend their winters, suggest that a lack of food is leaving the birds with little fuel for their long journey south. Perhaps, Peter suggests, they stopped to replenish the supplies along the way, or even decided to give breeding a miss this year and head straight for better feeding grounds in the Antarctic.

There have been, he says, reports of massive numbers of shearwaters found dead both along the eastern seaboard and, earlier in the year, in the northern hemisphere. Autopsies by the US Fish and Wildlife Service found that the birds had starved to death.

Its concerning because shearwater populations were only just recovering from a similar die off in 2013, and as they only have one egg a year, its a long, slow road to rebuild the population.

And as for the corpses littering the landscape, there’s no more positive answers. It could be, says Peter, the birds that have arrived are so weakened by their long flight and lack of food they die as soon as they land. Or maybe foxes, although the local authority has conducted control operations on the Island. He also posits wandering dogs or cats, but with no real enthusiasm.

The fact is that even though shearwaters are the most common migratory seabird, they only make landfall in the dark and head straight into their burrows, makes them very difficult to count. Hard data is difficult to find so no one knows the population size or dynamic.

Its all guesswork, according to Peter Barrand. But the birds are due to leave in April for their long flight back to the northern waters, and there’s no guessing how many will return next year. It could be the shearwater population goes from ‘most abundant’ to ‘in terrible trouble’ in the space of a couple of years, a truly terrifying thought.

But after the devastating loss of both birds and animals in the bushfires this year, and the concentration on saving those who survived, the fate of the missing muttonbirds is likely to remain on the backburner for some time to come.

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