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The Short-Tailed Sheerwater

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Matt Smith:

Welcome to the La Trobe University Podcast. I will be your host, Matt Smith, and I’m here today with Mark Carey from the Department of Environmental Management and Ecology. Thank you for joining me Mark.

Mark Carey:

Excellent.

Matt Smith:

You’re here today to tell me about what you’ve been researching, which is a bird called the short-tailed shearwater. It’s more commonly known as the muttonbird, though. Is that right?

Mark Carey:

That’s right. Most people know it as the muttonbird. Short-tailed shearwaters are a 600-gram, medium sized seabird. Their wingspan is about a meter and they are related to the albatross as part of that family.

Matt Smith:

What sort of background does this bird have? Why is it called a muttonbird to start off with?

Mark Carey:

I believe it’s to do with either their smell, they're quite a musty odour; that’s also referring to their tastes; it tastes like mutton. The Aborigines used to eat is a food source before European settlement but also colonial settlers used to take large numbers of hatched chicks and eggs.

Matt Smith:

Does this still happen, that sort of thing?

Mark Carey:

They take about 300,000 short-tailed shearwater chicks each year.

Matt Smith:

Who’s they?

Mark Carey:

They are the indigenous people of Tasmania. They have a right to harvest birds. Most of the birds are exported to markets in Melbourne and Tasmania, but also Perth in South Africa where they eat a lot of birds.

Matt Smith:

And whereabouts is their range, what’s their habitat at the moment?

Mark Carey:

The largest breeding population in the Furneaux group in Northeast Tasmania, but they also range from New South Wales, Victoria, into south Australia, all around Tasmania and there’s also an isolated population in Western Australia.

Matt Smith:

And what is it about these birds that you decided OK, you want to research these birds?

Mark Carey:

Well, I think they're really interesting because they are long lived, they form long term pair bonds, they attend to the same nest year after year, so they’re quite easy to study. Each year they would lay only one egg and if they lose it, that’s it. They have to come back next year to try again. But it’s also Australia’s most well-studied species. So we already know a lot about them, but there’s also quite a lot that we don’t know and so I was really interested in filling those gaps.

Matt Smith:

One every year?

Mark Carey:

That’s right.

Matt Smith:

So when you say long lived, what’s the general life span?

Mark Carey:

I think the record is 39 years.

Matt Smith:

Is that in captivity though?

Mark Carey:

No, that’s in the wild so all of this data are from banding studies. It was actually one of the earliest birds to be band in Australia in 1912 along with White-faced Storm-petrels. The greater emphasis was put on the banding program in the 1940s to look at longevity, migration, dispersal and nest side fidelity.

Matt Smith:

What aspect are you researching? Where is your work coming to it?

Mark Carey:

Well, my PhD is looking at the effects of investigate disturbance on these birds. I’ve conducted a few experiments looking at different handling regimes, patterns of divorce in relation to their reproductive success, and I’ve also attached data loggers to the birds to track their migration.

Matt Smith:

And what has that shown you?

Mark Carey:

This is a collaboration project with the British Antarctic Survey, and I’ve attached 27 loggers in 2007 and I retrieved 20 in 2008. So they were attached for 12 months. So, I travelled to Cambridge last year and to download these data loggers and produced maps. I chose a full 12-month migration of these birds. After they finished breeding, they leave the Furneaux group, they head south below the Antarctic convergence to feed and I called it a post-breeding dispersal. They feed, took down enough body reserve so they can migrate. And once the migration starts below New Zealand, they go straight up the Western side of the Pacific to the coast of Japan, closer into the Bering Sea. And that takes about 12 days, which is quite incredible. I mean, for a small, 600-gram bird to travel that far. It's quite incredible.

They spend much of their off-shore winter in the Bering Sea or off the coast of Japan. And on their return migration, they come down to the central part of the Pacific, hit the Australian coast around Queensland, New South Wales, travel down the coast back to the colony.

Matt Smith:

Was this the sort of migration pattern that you'd expected?

Mark Carey:

No. There've been two theories of migration previously, one from a banding study by Dominic Serventy, who started the banding program in 1947. And from his band recoveries, he suggested that after rain, they move across to New Zealand straight up the western side of the Pacific to Japan and the Bering Sea.

But on their return migration, he suggested that they skirt along the Californian coast of North America and come through the Pacific from there. Then in the '80s, a Japanese group were doing oceanic transits of the Pacific and they suggested broad movements on the Western side of the Pacific and then the return journey through the Central Pacific.

My data shows that after breeding they actually go to the Antarctic convergence to fuel up for a couple of weeks. Then the migration starts from there through the Western side of the Pacific, spending their winter in the Bering Sea. And their return journey is nowhere near the Californian coast, which Dominic Serventy suggested, but is actually more closely aligned to the Japanese theory.

Matt Smith:

And so, given that they are a small bird, it's almost logical that they would come down around California and kind of land-hop their way back around. But instead they cut right through the middle. Are they island hopping? Do they stop over in Hawaii?

Mark Carey:

No. One of the definitions of a true seabird is they only come to land to breed. So they are only actually on land when they're breeding in the Furneaux group or around that coast of the Australia. When they're migrating and when they're in a non-breeding period, they never come to land. They just sit on the water or they're flying or feeding.

Matt Smith:

Where have you been going to research this? Is there an island between Tasmania and Victoria that you've been going?

Mark Carey:

That’s right. I've been going down to the Furneaux group, which is in North-eastern Tasmania. And my study site is Great Duck Island. It's about 377 hectares, it's uninhabited and it's Tasmania's third largest muttonbird rookery.

Matt Smith:

Do you go there very often?

Mark Carey:

I've been going down there for the last six years. I actually calculated the other day that in the past six years I've spent over 12 months of my life down there.

I spent up to four months a year down there during the egg-laying incubation and chickering periods and so November to mid-January and then a couple of weeks in March, just before chicks flitch. And I've been involved with other projects on Pacific coasts and Senegal.

Matt Smith:

Do you have to take all your food with you? So, what sort of life is that like for a few months there?

Mark Carey:

Previously, I had access to a boat so I could go to the nearest town lay down, collect food, fuel for the generator, a drop of old fuel systems, get the local paper. On the island, there's no TV; we just have the radio. So all of our sort of outside information comes from there. But the hut is well-equipped with a gas stove and a gas fridge and plenty of rainwater tanks.

We have roughly a minimum of one other person with me, but we've had up to five or six other people. So it just fluctuates, depending on what research is being conducted.

Matt Smith:

How did the birds take the intrusion, so to speak, onto their island?

Mark Carey:

It certainly is their island. There are burrows right up to the back door basically of the hut. So at night when the birds come in, you can actually hear them scratch out their burrows and call to their partners. So it's quite a noisy experience at night and it takes a couple of weeks to get used to before you can actually sleep through it.

Matt Smith:

What have you been able to observe while you were on the island?

Mark Carey:

Every bird has their own personality. They nest in burrows, so I need to put my hand on the burrow and pull them out. You can get really quiet, gentle birds and then hit really aggressive that would absolutely tare your hands to bits. I've got a number of scars to show you how aggressive these birds are.

Matt Smith:

You showed me on the map where you've had the birds that are tagged. Why is there a series of dots going along the side of Antarctica there?

Mark Carey:

That was a bird that failed in February. He lost his chick in migration or it just died. So he went down to Antarctica instead of moved in a Westerly direction, almost the tip of Africa, and then he just came back to the Furneaux group and then started the migration. He had lost his chick. He had no reason to stay at the colony, so he just went on a little…

Matt Smith:

He went on some time out.

Mark Carey:

He had some time out, yes.

Matt Smith:

So they sound like very nurturing birds, then.

Mark Carey:

Well, they only have one egg a year and after that, that's it. So they really need to put a lot of investment into their chick-rearing. They need to provision their chicks for up to three months so it can survive. Yes, you can say they are nurturing because they need to look after their chick.

Matt Smith:

Are they an endangered species?

Mark Carey:

No. They're actually one of Australia's most populous birds. There's an estimated 23 million short-tailed shearwaters. That's just breeding birds and there's probably another several million non-breeders. In the Furneaux group alone, there's 11 million breeding birds on the islands.

Matt Smith:

Well, I suppose it's due to that number of birds that they're allowed to be harvested, I suppose.

Mark Carey:

That's right. Each year this commercial license is to take around about 300,000 chicks. And it's actually one of a few examples of a sustainable harvesting of wild bird.

Matt Smith:

What's next on the agenda? Is there any sort of aspects about the bird that you want to research, or are you going on to another bird?

Mark Carey:

Well, this is part of my PhD and I hoped to hand it in around September, October later this year and I would love to stay in research, particularly seabird research. I would be more than happy to stick with this bird because there's so much we don't know. I would love to do some more research on their migration. But also there are an equal number of birds that we have no knowledge about. So, I really like to get into some of those birds as well.

Matt Smith:

Another thing that you've been researching is how birdlife is affected by plastics that we throw away and that we dispose. And this is a big problem with seabirds, isn't it?

Mark Carey:

That's right. Seabirds and plastic congestion of synthetic material is a serious problem. Research has been going on since the '70s, but increasingly more species are getting affected. The Laysan Albatross on Midway Island are just full of plastic material, mainly user plastic like cigarette lighters, bottle tops, but also industrial resin pellets which is used for moulding plastic. And that's having serious consequences on a bird's breeding condition and they often die because of it.

Matt Smith:

What have you found? You've been going out to the field to do this. Tell me about it. Where did you go and what were you looking for?

Mark Carey:

Recently, I went to Phillip Island just as the short-tailed shearwater chicks were fledgling. And I was collecting beach-washed fledglings and I was dissecting their proventriculus and gizzard out of these birds, which is kind of like just their stomachs. I was prepping them up and I was collecting plastic pellets and plastic pieces inside their stomach.

Matt Smith:

So were these birds dying from ingesting a plastic?

Mark Carey:

These birds were dying from natural causes. These were beach-washed birds, so they basically hit the water, died, and washed up from the beach. And I was just going along the beach on Phillip Island.

Matt Smith:

Just when they first come out of the nest.

Mark Carey:

That's right. So these birds are fledgling at this time of year, the end of April, early May. They come out of their burrow, they exercise their wings. They attempt to take off. Some make it and some don't. Most don't, they hit the water and died basically. So I was taking that opportunity to collect the birds, dissecting them and I can get a feel for how much plastic is in these birds.

Matt Smith:

These are baby chicks, very young juveniles. How are they getting plastic in their stomach?

Mark Carey:

They've never been out of the nest before, so their parents are bringing back plastic in their food. Parents are flying off, they're feeding, they're bringing back plastic collected during their feeding exercise and feeding that to chicks.

Matt Smith:

What sort of percentage did you have of chicks that actually have plastic in their stomach?

Mark Carey:

The stomachs I dissected on Phillip Island, 80 percent had plastic in their proventriculus. But more particularly, they're stuck at their gizzards.

Matt Smith:

That sort of plastic isn't going to go away, is it? That's with the bird for life, really.

Mark Carey:

No. Once it gets to the gizzard, it's very difficult for the bird to get rid of it unless it deteriorates through the gizzard stones. With enough material, it can cause PCV concentrations to go up and that could affect potentially body condition or growth, and it could also affect their productive biology.

Matt Smith:

And they can have ruptured stomachs as well, can they?

Mark Carey:

Absolutely. There are a number of sharp plastic and that has the potential to perforate the proventriculus.

Matt Smith:

Is there something that people should be doing so this sort of thing could be prevented, not throw away plastics?

Mark Carey:

Yeah, absolutely. One of the biggest things I was finding on the beach was the use of plastic like bottle tops, bottles, cigarette lighters. All these things, they don't go into a proper refuge, go into our oceans and potentially cause a significant damage to our marine life.

Matt Smith:

And you're finding these sort of things in chicks, were you?

Mark Carey:

That's right.

Matt Smith:

Wow, that's really terrible stuff. Mark, thank you for your time today.

Mark Carey:

Thank you.