Shearwaters have one of the most incredible migratory lifecycles of all our seabirds - and the Far South Coast is a prime location to see it in action.
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Barunguba (Montague Island) has one of the world's longest continuous seabird studies.
Researchers have been visiting the island near Narooma since the 1960s, focusing on shearwaters.
This week more than 18 million short-tailed shearwaters returned to Australia to breed after flying 15,000 kilometres from the Northern Pacific waters of Alaska and Japan.
Amy Harris, National Parks and Wildlife Service ranger for the Eurobodalla area, has worked for the NPWS since 2001 and been a ranger on the island since 2017.
"Our short-tailed shearwaters synchronously arrive and breed," Ms Harris said.
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Mind-boggling life cycle
Each year they re-excavate their burrows, which can be up to two metres long, mate and start nesting.
They lay a single egg in late November and the male and female take turns incubating the egg and feeding the chick.
"There is a lot of effort so both have to be involved to ensure the chick's survival," she said.
Usually by January chicks are hatching in the burrows.
That's when the hard work begins.
One adult will make a 15,000km round trip to the Southern Ocean near Antarctica to feed on the rich krill.
The trip can take up to three weeks.
They do these amazing migrations to put themselves where the food hot spots are.
- Amy Harris, NSW NPWS Eurobodalla Area
In the meantime the chick needs feeding so the other adult does shorter trips every day or every second day to get food.
"From putting trackers on them, the researchers found they can do speeds of 80 kilometres per hour and fly up to 1000 kilometres per day," Ms Harris said.
"The researchers were blown away."
When the adult returns from the Southern Ocean with a belly full of very nourishing krill, it regurgitates it into the chick's mouth. The adults then swap duties.
Truly global birds
They are coined the eternal summer seabirds because they are always chasing the summer.
The adults depart in April, leaving their chicks in the burrows to grow their final flight feathers and turn fat into muscle.
However, the chicks still end up in the same areas as the adult.
"They breed, feed and migrate totally by instinct."
With a life span of around 20 years, short-tailed shearwaters undertake their annual migration many times.
Because they winter in the northern hemisphere and are influenced by currents and food availability there, "they are a really important bird to monitor because they provide insights into the global perspective into food resources and prey availability," Ms Harris said.
"The International Union for Conservation of Nature recognises their numbers are in decline, but we need to do more research to find out what is causing that."
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