OPINION: The fate of the Shearwaters of Muttonbird Island


DEAR News Of The Area,

THE recent Prime News report entitled ‘Shearwater Breeding Crisis’ on May 14 is no surprise.

The devastating lack of chicks was caused mainly by rats and not by recent rain, people or the lights of Coffs Harbour, or a global food shortage.

These birds have survived for centuries through good and bad seasons.

The start of a Shearwater population decline was 25 years ago with the introduction of native swamp rats in the 1995-6 season.

Based on burrow counts the decline has been 80%.

I have been documenting the changes in shearwater numbers and the vegetation since I saw the first distinctive rat grazing pattern on 12 April 1996.

The rats depend for food and water almost exclusively on the succulent plant Commelina where the best shearwater burrows are found.

Rats use shearwaters burrows and make extra holes in the burrows making them unsuitable for raising healthy chicks.

They eat eggs from under the sitting birds.

Around 2000 bluetongue lizards were found on the island; they also eat eggs.

This last season in October 2020 we saw the rat numbers increasing and starting to use and damage the shearwater burrows.

In late November when the birds came to lay (they can only lay one egg a year) most of the burrows in the areas where there was Commelina had been damaged.

We found bite marks on eaten eggs indicating some were rats, some lizards.

I estimated only 10% of burrows were left with eggs in January.

The rain probably contributed to further breakdown of burrows.

It was not surprising that there were only 20 stranded birds rescued in April.

Without drastic remedial action now, when the current adult birds die, there are no young birds to replace them.

This will mean that this island, once the most densely populated in NSW, will have no shearwaters.

Having healthy shearwaters chicks raised on this island in the future requires removing all rats and lizards now.


Narelle SWANSON,
Bird Bander and Shearwater Researcher.

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