The Pacific gull – in crisp black-and-white plumage with bright orange and yellow bill – has long been regarded as the most beautiful of Australia’s gulls.
Because it is largely a marine species it has avoided the tag of “garbage gull”, a fate befalling the silver and kelps gulls which love to scrounge food at fish punts on Hobart’s waterfront.
The Pacific gull might have a squeaky-clean image in Tasmania’s south but its behaviour in the Derwent Estuary seems to be at odds with that of the species further north.
Researchers studying the gull’s feeding behaviour in Launceston have been startled to discover its diet there is so spiced with food waste that the species has now joined the “flying trash bin” brigade.
In my own citizen-science observations of Pacific gulls, they have always presented themselves as a cut above the rowdier, less delicate, kelp and silver gulls. The Pacific gulls always appear to keep their distance from the others. Also, I’ve only seen individual Pacific gulls among the vast flocks of kelp and silver gulls on the rubbish tips of the Hobart area during BirdLife Tasmania’s winter gull counts.
In the north it is a different story. The research by the University of Tasmania’s Institute of Marine and Antarctic Studies has revealed the gulls of the Tamar River are ingesting levels of plastic which are not only a danger to themselves, but to the marine environment.
The research published in the Marine Pollution Bulletin focused on the regurgitated pellets, called boluses, of a population of Pacific gulls roosting on the Tamar Island wetlands.
Lead author Lillian Stewart said studying boluses gave scientists valuable data on gull foraging behaviour.
“These wetlands are pristine, yet we found that over 90 per cent of the boluses we collected contained one or more items of human-generated debris like plastic, glass or metal, and almost 87 per cent contained at least one item of plastic,” she said. The rates were among the highest for any gull species globally.
The boluses collected from the roosting site were a mixture of “unnatural” debris, including items like personal hygiene products, dental floss picks, bread-bag clips and rusty nails.
“The extent to which anthropogenic debris now dominates the diet of these birds is staggering. We found that only 7.49 per cent of Pacific gull boluses were composed entirely of natural items,” Ms Stewart added. “These are all indicative of household waste, and are likely to have been acquired from landfill.”
Co-author Dr Jennifer Lavers said the transfer of debris, especially single-use plastics, from the land to the sea had become so common that seabirds were being referred to as ‘‘flying trash bins’’.
The research showed that better waste management at landfill sites was needed to reduce the harmful debris available to wildlife, and thus to prevent it being transferred to the ocean.