Migrating Seabirds 

Migration Challenges

The migratory species WIRES has historically received the most calls about has been shearwaters (also known as muttonbirds), primarily short-tailed shearwaters and wedge-tailed or sooty shearwaters from Australian or New Zealand breeding grounds.

Short-tailed shearwaters are amongst the world's most populous bird species. However mortality rates during migration can be very high as their annual migration is one of the longest of any bird, approximately 15,000 kilometres.

Despite these mortalities occurring each year, short-tailed shearwaters remain one of the most populous bird species in the world and when you consider the incredible number of birds that migrate each year (estimated at over 20 million individuals that mostly migrate successfully and invisibly without coming to land), the number of fatalities is comparatively small. 

Each year millions of young shearwaters are added to the population, despite the challenges they face. Short-tailed shearwaters leave their Bass Straight breeding grounds in late April-early May, fly north east across the Pacific Ocean and on to the Bering Sea between Russia and Alaska to spend the Australian winter in the northern hemisphere. On this northern migration they live almost constantly on the wing, and for the new generation this is their first migration. The southward migration can be broken by some feeding stops while returning to their breeding grounds via the east coast of Australia, to breed in late Spring and Summer.

Unfortunately, mortality is a natural part of these long migration events particularly for immature birds during their first migration, and can sometimes present as ‘wrecks’, where hundreds of dead birds are found washed up on beaches along the coast of NSW. These large-scale mortality events typically coincide with unusually warm sea temperatures in the East Australian Current. On their southward migration shearwaters rely on food resources such as krill, crustaceans, squid and fish and warm sea temperatures on the continental shelf can push their preferred diet further offshore, leading to starvation.

A shearwater can lose almost half its body weight during the long migration so the chances of survival once washed ashore are very low. Rehabilitation and recovery of shearwaters that are depleted following their long migration is extremely difficult and mortality is very high, even when taken into care. Birds may be suffering emaciation, dehydration or metabolic dysfunction, all of which are very difficult to reverse and treat.

With H5 bird flu now also a major concern for wild bird populations, people should avoid handling sick or dead birds unless necessary and appropriate precautions are taken. With shearwaters it is also very important not to disturb the oil coating on their feathers.

Any deceased shearwater, or live shearwater displaying clinical signs of H5, must be reported to the Emergency Animal Disease (EAD) hotline via 1800 675 888. If you see unwell shearwaters please keep people and animals away from them where possible and report the sighting to the EAD as instructed above.

If you are unsure what to do when you see sick, injured, or orphaned wildlife, call WIRES for advice on 1300 094 737.

Muttonbird Island Nature Reserve

Separate to the annual migration event, there is an island off the coast of NSW that is home to thousands of wedge-tailed shearwaters. Muttonbird Island near Coffs Harbour in NSW, is where thousands of wedge-tailed shearwaters reside for part of the year.

The birds spend the Australian winter in southeast Asia, travelling back to Muttonbird Island in August each year. They depart on their annual migration in late April every year. Fledglings, when attempting to leave the island to begin their migration for the first time may become disorientated and confused due to artificial light from the mainland.

In these instances, if uninjured, they will need to be contained and returned back to the island where they will have a second chance at a successful take-off.

If you are unsure what to do when you see sick, injured, or orphaned wildlife, call WIRES for advice on 1300 094 737.