They spend 6 months breeding in south eastern Australia over the summer. This is the first leg of an annual migration that can span up to 30,000 kilometres – one of the longest made by any bird in the world.
Their migratory path is quite difficult to accurately track as they don’t come to shore during their migration. Studies suggest the majority of birds fly north along the western part of the Pacific Ocean to the Arctic region in April and May, before returning southwards through the centre of the ocean to Australia to breed in late spring and summer. They have been known to fly this enormous distance in only six weeks.
As you can imagine they need a huge amount of energy to migrate such long distances and this is stored in the form of body fat. Many birds lose up to half their body weight during this long and arduous journey. Sadly, thousands of birds die each year from starvation and exhaustion during their journey that takes them through some of the world’s harshest weather conditions. The mortality rate for fledglings is very high with up to 50% not making the return journey.
In 2013 large numbers of dead, exhausted and emaciated birds washed up on Sunshine Coast beaches. As alarming as this may have appeared, it was a natural event and is referred to as a wreck. One of the first reports of last year’s wreck came from fishermen travelling into the Mooloolaba harbour and encountering a sea of mutton birds in the water. This was shortly followed by thousands of birds found stranded on the beaches and rocky outcrops, looking for shelter and rest. Council recorded and collected over 12,000 deceased birds on beaches from Caloundra to Teerwah.
Some of the birds that washed ashore on beaches were alive but died shortly afterwards. Researchers from the University of Queensland research station have found stranded shearwaters extremely difficult to rehabilitate due to the severe muscle wastage they suffer on their 15,000km outward journey to Australia.
During the clean-up of the wreck we were fortunate to come across a shearwater at Point Cartwright that had an Australian bird and bat banding scheme (ABBBS) tag on its foot. The shearwater was tagged as a nestling in March of 2002 by Professor Ron Wooler from Murdoch University at Great Dog Island in the Bass Strait. The shearwater is likely to have migrated from the southern to northern hemisphere each year of its life. This equates to an incredible distance of around 165,000km.
The Shearwater is Australia’s most abundant seabird with about 23 million short-tailed shearwaters breeding in colonies in south eastern Australia from September to April. Many of the colonies are showing a marked decrease in numbers. Although reports suggest there are still large numbers in existence, they are slow breeders, laying only one egg each year. If this situation is left unmanaged, their numbers could drop dramatically due to the dangers they face on their annual migration, as well as through harvesting by humans and loss of habitat.
The information that was collected over the past few months on the local wreck has been submitted to the Australian Wildlife Health Network, ABBBS and BirdLife Australia. This will add to the vast amount of data collected by many councils and environmental groups that monitor the plight of the shearwaters.
The name shearwater is derived from the fact that they have the ability to cut or shear the water with their sickle-shaped wings which look seemingly motionless when they fly. Their other name muttonbird was given to them by early European settlers, who killed these birds for food and found that their flesh tasted like sheep or mutton (flying sheep).