Plastic debris has been found in more than 80 per cent of the nests of a species of seabird on an uninhabited island off the coast of Scotland.
Surveys on Lady Isle in the Firth of Clyde revealed plastic in the nests of European shags (Phalacrocorax aristotelis), which breeds around rocky coasts.
As well as the shag, 35.6 per cent of herring gull nests and 53.5 per cent of great black-backed gull nests contained plastic, as well as two other species.
In total, almost 40 per cent of nests surveyed on Lady Isle contained plastic, with the amount varying between species.
Plastic in nests has been identified as coming mostly from consumer waste such as bottles and food packaging thrown away in built-up areas.
This is then transported to nest sites by the sea’s strong currents rather than by the birds themselves, the researchers report.
A European shag on Lady Isle. Plastic debris has been found in 80 per cent of the bird’s nests on the uninhabited island off the coast of Scotland
Lady Isle is a small, uninhabited island, in the Firth of Clyde, Scotland. For many years it was leased out as a bird sanctuary with a bird observatory and warden’s post built and run by the Scottish Society for the Protection of Wild Birds (SSPWB)
‘They end up in seabird nests, not because seabirds actively pick them up in built-up areas and carry them to their nest, but because are brought there passively by marine currents,’ said Dr Ruedi Nager, a seabird ecologist and senior lecturer at the University of Glasgow.
For the survey, which was carried out in May 2018, researchers examined 1,597 nests on the island off the Ayrshire coast, of which 625 contained some plastic.
Plastic in the nests ranged from sheets, threads, hard fragments and foamed synthetics and ranged in colour from transparent to pink.
The research, led by the University of Glasgow, suggests plastic is being washed ashore from nearby Ayrshire, including the towns of Prestwick, Troon and Ayr.
Once it reaches Lady Isle, it is incorporated into the birds’ nests – at which point it becomes a potentially lethal tangling hazard.
Plastic in nests could also affect the quality of nests structures, which could be detrimental for eggs and chicks.
The large difference between plastic proportions in the nests of shags and herring gulls may be due to their different nest-building behaviours.
Because shags reuse their nests year after year, the proportion of plastic in their nests likely builds up over time.
Herring gull nest with plastic on Lady Isle. Surveys found that more than a quarter of all nests on Lady Isle contained plastic, with the amount varying between species
Gulls, meanwhile, make new nests each year from materials local to the nest site.
Amongst the other species surveyed, 24.8 per cent of nests belonging to the great cormorant (Phalacrocorax carbowhile) had plastic traces, and 25 per cent for lesser black-backed gulls (Larus fuscus).
Danni Thompson, a researcher volunteering with Dr Nager, looked more closely at the herring gull, the most abundant species nesting on Lady Isle.
‘As herring gulls often forage in landfills, we wanted to see if they were swallowing plastic whilst eating and then bringing it back to the nest,’ she said.
‘Seabirds interact with plastic via ingestion, entanglement and nest incorporation but we know little about who, what, why and how.
‘In herring gull nests it was sheet plastic – mostly off-white/clear or blue-purple.’
The five species surveyed and the proportion of these species’ nests on the island containing plastic. From left, European herring gull (Larus argentatus); Lesser black-backed gull (Larus fuscus); Great black-backed gull (Larus marinus); European shags (Phalacrocorax aristotelis) and Great cormorant (Phalacrocorax carbo)
The study also mapped all nests on Lady Isle to see whether nests with plastic were equally distributed across the island.
Nests on the north of the island, which are closer to the outgoing tide from the mainland, were more likely to contain plastic, they found, suggesting it came from the mainland and was washed up on the shore.
The research also concluded that plastic was not ingested at foraging sites and regurgitated while the birds were in their nests.
Plastic types from some regurgitated food remains were different from those found in the nest, suggesting plastic in nests arrived by different means.
The scientists said further research is needed to identify whether or not plastic presence in nests has an impact on seabird populations.
Identifying the potential sources of plastic could also help conservationists to plan action such as targeted beach cleans to reduce the impact on birds.
Herring gulls on Lady Isle, which faces the west coast of Scotland and towns including Prestwick, Troon and Ayr
‘Impacts of plastic in nests is unknown – it may alter properties and quality, and cause entanglement,’ said Thompson.
‘Long-term studies are vital for documenting change and we suggest recording plastic presence alongside existing monitoring.’
Seabirds are building and rebuilding their nests just now as Brits are in lockdown and the shores are quieter, which may mean less plastic waste.
‘It will be interesting to see what seabird nests are made of this season,’ Dr Nager added.
The research paper has been published in Marine Pollution Bulletin.