Short tailed shearwaters in V shaped flocks the size of Boeing 747s are winging their way across the Pacific Ocean towards the Gold Coast carrying an unwelcome payload.
They make landfall around the Gold Coast on their 15000km return from the Alaska to nesting grounds in Bass Strait this time every year, but new information has emerged about just how many of them are carrying plastic in their guts.
Two thirds of all Australia’s 28 million shearwaters have ingested plastic in the stomachs, the lead analyst of a three year marine debris research project says.
CSIRO Senior Research Scientist Chris Wilcox says one of the most surprising findings of his analysis was how much plastic and debris is in shearwaters and animals in general.
A key concern coming out of the project is that as marine debris increases the impact on marine fauna increases through entanglement, ingestion and chemical affects.
“Plastic production rates are intensifying, and the volume of refuse humans release into marine systems is growing at an exponential rate,” the report says.
Shearwaters have a high debri load because of their surface feeding style, Chris Wilcox says.
They either mistake floating plastic for food or eat it because it has fish eggs attached, he says.
For the last three years, CSIRO with partners Shell Australia’s National Social Investment Program and Earthwatch surveyed the entire Australian coastline both on the beach and in the ocean to produce the report Understanding the effects of marine debris on wildlife, which has just been released.
The report’s lead analyst Dr Wilcox says the findings don’t say what negative impacts the debri load has on the birds, but it is safe to say plastics aren’t having a positive impact. They eat everything from balloons to glow sticks, industrial plastic pellets, rubber, foam and string.
He says the wreck events like the one last year when thousands of shearwaters washed up dead or dying on Gold Coast beaches happen naturally because of food shortages and weather, but marine birds might eat more plastic when food is low as they become hungrier.
His analysis included a global risk analysis of seabirds and marine debris ingestion for nearly 200 species and found that 43 percent of seabirds and 65 percent of individuals within a species have plastic in their gut.
Disturbingly this is projected to increase to 95 percent by 2050.
He is surprised at just how much marine debris is on the Australian coastline even in remote areas – with a few thousand pieces per square kilometre in some places to up to 40,000 pieces in other places. One of the worst areas was inside the Great Barrier Reef after a flood and cyclone event.
The findings show that most marine debris is plastic and nearly all of it originates in Australia except for fishing nets in the Gulf of Carpentaria which is mainly of international origin.
“What we are trying to do is provide some database, some advice based on the data about how big the problem is and what actions might be effective in terms of reducing the problem,” Dr Wilcox says.
“Whether or not policy makers choose to take those up or not is outside of my purview.”
“The goal for us was to identify what policies at a council, state and national level would make a difference in terms of the amount of plastic going into the ocean.”
He says single use fizzy drink bottles are the biggest culprits and consumer habits and illegal dumping needs to change.
The report shows that shearwater nestlings being fed by mothers are at high risk from plastic particles in the regurgitated food mix. It also shows that young birds are also more at risk of ingesting plastic when they feed.
A member of the Australian Bird and Bat Banding Scheme, Phillip Du Guesclin, who has been banding shearwaters at a nesting ground in Port Fairy in South West Victoria for 30 years surveyed shearwater chicks in April and May before they left for the north. He couldn’t explain why there was an unprecedented low number of chicks in the count.
Mr Du Guesclin said he normally counts 50 to 150 nestlings just after the parents leave on migration in April but this year could only count 19. He said he didn’t know if they weren’t there in the first place or if they had left earlier than usual.
A Japanese migratory bird scientist, Senior Biologist for Yamashina Institute for Ornithology Nariko Oka, says there wasn’t a wreck of shearwaters along the Japanese coast this year in May during their migration north.
“In years of the poorest growth of chicks, fledglings probably die off on their way in the tropical or subtropical waters before reaching to mid latitude waters like Japan,” he says.
Dr Oka says warmer than usual temperatures in the Bering Sea at the end of July and early August could have reduced the krill that the shearwaters feed on in the north.
“Shearwaters will probably suffer on their migration back to Australia during the coming return trip, because of a decrease of food for them,” he says.