Each spring, millions of Short tailed Shearwaters return to Tasmania after spending months at sea in the northern Pacific Ocean. Known locally as muttonbirds, these seabirds undertake one of the longest annual migrations of any bird, travelling thousands of kilometres between their northern feeding grounds and breeding colonies in southern Australia.
Across the islands of Bass Strait and sections of Tasmania’s coastline, breeding colonies become active once again. Some support hundreds of thousands of birds, with adults gathering offshore before flying inland after dark to occupy their nesting burrows and begin another breeding season.
Short tailed Shearwaters also have a long history of cultural significance in Tasmania, particularly for Aboriginal communities whose connections to muttonbirding continue today. Their annual return is part of a remarkable life cycle shaped by long distance migration, breeding on Tasmania’s coast and the challenges of surviving across the Pacific Ocean.
A Familiar Visitor to Tasmania
The Short tailed Shearwater (Ardenna tenuirostris), also known as the muttonbird or moonbird, belongs to a group of seabirds named for their distinctive flight close to the ocean’s surface, where their outstretched wings appear to skim the water.
Measuring approximately 40 to 45 centimetres in length, with a wingspan of around one metre, Short tailed Shearwaters are medium sized seabirds with predominantly dark brown plumage that can appear almost black at sea. They have long, slender wings, a relatively short tail and a dark, hooked bill. Their colouring and overall shape can make them difficult to distinguish from other shearwater species, particularly when viewed at a distance or among large flocks moving across the water.
Tasmania supports some of the world’s largest breeding populations of Short tailed Shearwaters. Colonies are found on offshore islands throughout Bass Strait and along sections of the Tasmanian coastline, with birds occupying coastal grasslands, headlands and other areas where suitable nesting habitat is available.
Built for Life at Sea
Short tailed Shearwaters are highly adapted to life on the open ocean. Their long, narrow wings allow them to make use of winds above the waves, alternating between rapid wingbeats and gliding as they travel close to the water’s surface.
They feed primarily on krill, small fish and squid, often gathering in large flocks where prey is abundant. While they can take food from the surface, Short tailed Shearwaters are also capable divers, using their wings to propel themselves underwater in pursuit of prey.
Like other members of the petrel family, Short tailed Shearwaters possess specialised salt glands above their eyes. These glands help them excrete excess salt, allowing the birds to consume seawater and obtain moisture from marine prey without relying on freshwater sources. Their sense of smell may also help them locate productive feeding areas, although research into the role of chemical cues has largely involved other petrel and shearwater species.
Their adaptations to life at sea come with some limitations on land. With legs positioned towards the rear of their bodies, Short tailed Shearwaters are less agile when walking and may scramble across coastal vegetation or exposed ground before reaching their nesting burrows. Swimming, diving and flying are far better suited to their anatomy than moving about on land.
One of the World’s Great Migrations
Every year, Short tailed Shearwaters undertake one of the world’s great bird migrations, travelling between their breeding colonies in southern Australia and the northern Pacific Ocean. Their journey takes them across the equator, with birds covering approximately 15,000 to 17,000 kilometres in each direction.
Their route is not a simple journey north and back again. After leaving Tasmania in autumn, some shearwaters initially head south into the Southern Ocean, where they spend several weeks feeding beyond the Antarctic Polar Front. From there, they travel north through the western Pacific, passing towards Japan and continuing into waters around the Bering Sea and other northern feeding areas. During the Northern Hemisphere summer, birds may remain in these productive waters for several months, moving between feeding areas as conditions change and prey becomes available.
The return journey generally takes them south through the central Pacific Ocean. By late September and early October, the first birds begin arriving back at their breeding colonies in Tasmania and elsewhere in southern Australia.
Much of what scientists now know about these movements comes from tracking technology. In a 2014 study, researchers fitted geolocators to Short tailed Shearwaters breeding on Great Dog Island in Bass Strait, allowing them to follow the birds’ movements beyond the breeding season. The results revealed a previously undocumented Southern Ocean stopover and showed that individual birds differed in the timing and extent of their northern movements.
The distances covered during these journeys are substantial. The same study recorded birds travelling an average of approximately 10,920 kilometres in just 13 days during their northward passage across the Pacific, equivalent to around 840 kilometres a day. These findings demonstrate how rapidly Short tailed Shearwaters can move between distant feeding areas during their annual migration.
The Extraordinary Migration of the Bar tailed Godwit
Another remarkable long distance traveller, the Bar tailed Godwit undertakes some of the longest nonstop flights recorded in the bird world. During its annual migration between Alaska and Australia, this shorebird can travel more than 13,000 kilometres across the Pacific Ocean without stopping to feed or rest, making its journey one of the most extraordinary feats of endurance in nature.
A Few Things You Might Not Know
They can find their way back to the same burrow. After spending months travelling across the Pacific Ocean, breeding Short tailed Shearwaters often return to the same colony and nesting burrow. Established pairs may also reunite across successive breeding seasons, although precisely how these birds navigate such enormous distances remains an area of scientific research.
Their chicks can become heavier than their parents. Young shearwaters accumulate substantial fat reserves during the breeding season, sometimes becoming heavier than the adults feeding them. These reserves help sustain the chicks after their parents depart, before they eventually leave their burrows and begin feeding independently.
They have tubular nostrils. Like other members of the petrel family, Short tailed Shearwaters have distinctive tube shaped nostrils on the upper surface of their bills. This feature is characteristic of a wider group of seabirds known as tubenoses, which includes petrels, albatrosses and shearwaters.
Their breeding colonies come alive after dark. During daylight hours, many adults are away feeding at sea or resting inside their burrows. After sunset, the colonies can become remarkably noisy, with birds calling to their partners and communicating around their nesting sites.
They take years to begin breeding. Although young Short tailed Shearwaters leave their colonies during their first autumn, they do not immediately return to raise chicks of their own. Long term research on Fisher Island in Bass Strait found that birds first began breeding at five years of age, with some not breeding until considerably later.
Returning Home to Breed
Short tailed Shearwaters begin arriving at their breeding colonies in late September and early October, returning to nesting areas used in previous seasons. Their burrows are excavated in soft soil, often beneath coastal grasses and shrubs, where the underground chambers provide shelter from the weather and some protection from predators. Returning birds may tidy existing burrows or excavate new ones before the breeding season begins.
Egg laying generally begins in late November, with each female producing a single white egg. Both parents share incubation duties over approximately 53 days, taking turns remaining at the nest while the other feeds at sea. The chick usually hatches in January and remains inside the burrow throughout its development, dependent on food brought back by the adults.
Raising a chick requires months of repeated feeding trips. Adults travel between the colony and feeding areas at sea, sometimes covering considerable distances before returning with food. As the chick grows, it develops its flight feathers and accumulates the energy reserves needed to survive the period between its final meals and departure. Breeding success can also be affected by local conditions, including heavy rainfall that floods or damages nesting burrows.
By April, adult shearwaters begin leaving their breeding colonies for the northward migration. Their chicks remain behind, completing their development before emerging from the burrows and making their way towards the ocean. They must then begin feeding independently and undertake their first migration without parental guidance.
A Long History of Muttonbirding
Short tailed Shearwaters have been harvested for food in Tasmania since long before European settlement. Known widely as muttonbirds, they hold particular cultural significance for Tasmanian Aboriginal people, especially families with longstanding connections to the islands of Bass Strait. Harvesting these seabirds forms part of a broader history of Aboriginal relationships with Country, seasonal food resources and the coastal environment.
Muttonbirding remains an important cultural practice for many Tasmanian Aboriginal families. The annual harvest provides opportunities to return to the islands, maintain connections to Country and pass knowledge between generations. These visits are about more than collecting birds for food, bringing families together and continuing traditions that have survived generations of profound social and cultural change.
Commercial harvesting developed during the nineteenth century, particularly on islands in Bass Strait where large breeding colonies provided a seasonal source of food and income. Muttonbirds were harvested for their meat, oil and feathers, with Aboriginal families playing a significant role in the development and continuation of the industry. For some island communities, muttonbirding became an important part of seasonal employment and household income.
Today, muttonbirding remains a regulated activity in Tasmania. Commercial and recreational harvesting are subject to licensing and seasonal restrictions, with the taking of chicks generally occurring during autumn, before the young birds would naturally leave their burrows. Separate arrangements recognise Aboriginal cultural harvesting, including provisions allowing traditional practices on designated Aboriginal land without a permit or licence.
Harvesting restrictions and population monitoring are part of the contemporary management of Short tailed Shearwaters in Tasmania. Annual monitoring helps inform decisions about harvesting, while some colonies remain closed to allow their populations to recover.
Why Short Tailed Shearwaters Matter
Short tailed Shearwaters play an important role in marine ecosystems across the Pacific Ocean. As predators of krill, small fish and squid, they form part of ocean food webs, while their breeding colonies also influence the coastal environments where they nest. Nutrients deposited through droppings and other organic material contribute to the soils surrounding their burrows, affecting local vegetation.
Despite their abundance, these seabirds face pressures across an enormous geographical range. Changes in ocean temperatures and currents can affect the distribution and availability of prey, particularly in the northern waters where they spend much of the non breeding season. In 2019, thousands of Short tailed Shearwaters were found dead along the coast of Alaska during a period of unusually warm ocean conditions. The mortality event raised concerns about food availability and changing marine ecosystems, although the presence of warmer water alone does not establish the cause of individual bird deaths.
Closer to Tasmania, breeding colonies face different challenges. Introduced predators, including feral cats and rats, can prey on birds and their chicks, while trampling and other human disturbance can damage nesting burrows. Coastal development, habitat degradation and changes to vegetation may also affect breeding areas, particularly where colonies occupy relatively small islands or narrow sections of coastline.
Marine plastic pollution is another documented concern. A Tasmanian study examining 171 Short tailed Shearwater chicks found plastic debris in 96 per cent of them, demonstrating how widespread ingestion can be even among young birds that have not yet left their breeding colonies. The researchers did not establish a significant relationship between the amount of plastic ingested and the chicks’ body condition, leaving questions about the longer term consequences.
The arrival of highly pathogenic avian influenza H5 in Australia during 2026 has introduced another concern. With millions of Short tailed Shearwaters returning to southern Australia for the breeding season, NRE Tasmania has emphasised the importance of monitoring seabird colonies and reporting unusual illness or mortality. Large breeding colonies bring birds into close contact, creating opportunities for infectious diseases to spread. However, the presence of H5 in Tasmania does not itself establish that Short tailed Shearwaters have been infected.
Protecting these birds requires attention to their breeding colonies and the marine environments they depend on throughout the year. Local conservation measures can reduce threats around Tasmania, but conditions across the Pacific also influence the survival of birds returning to breed each spring.
Witnessing Their Return
Each spring, Short tailed Shearwaters return to breeding colonies around Tasmania, with some of the most noticeable activity occurring after sunset. Large numbers may gather offshore before flying towards their nesting burrows, their distinctive calls carrying across the colonies as birds arrive in the fading light.
Visitors can observe shearwaters at several established locations, including the Bruny Island Neck viewing platform and The Nut State Reserve at Stanley. Other colonies occur along Tasmania’s coastline and on islands throughout Bass Strait, although access to some sites is restricted to protect breeding habitat. Visitors should check local access arrangements before travelling.
Nesting burrows are often hidden beneath coastal vegetation and can collapse underfoot, potentially injuring birds or damaging nests. Visitors should remain on established tracks, avoid entering nesting areas and keep dogs away from breeding colonies. Unnecessary artificial lighting should also be avoided, particularly when young birds are leaving their burrows for the first time.
Observing Short tailed Shearwaters from a suitable distance allows visitors to experience the activity of a breeding colony without interfering with the birds’ return to their nests.
Editorial Note: Wild Island is committed to publishing accurate, independently researched and evidence based wildlife information. Our articles draw on authoritative sources, including scientific research, government publications and information from relevant wildlife and conservation organisations. Sources are assessed and information is verified wherever possible before publication.
Cover Image by JJ Harrison / Wikimedia Commons / CC BY-SA 3.0.
