Scientists are trying to find out why some 20,000 guillemots have died in recent weeks along the Dutch coast.
The birds were all emaciated and there are fears they may have been victims of a spill from the MSC Zoe container ship, from which some 345 containers fell in the sea during a storm.
“There’s no smoking gun, but we’re looking into it,” says Mardik Leopold, who is investigating the deaths.
Chemicals may be to blame as most plastics are hard to ingest, he says.
Hours after the containers fell off the MSC Zoe in a storm, they started washing up on islands off the Dutch north coast on 2 January, spilling their contents of children’s toys, furniture and televisions on to the beaches.
A bag of peroxide powder was also found.
Why were so many birds affected?
Mardik Leopold, a seabird expert from Wageningen University, said the figure of 20,000 dead guillemots was based on educated guesswork.
“That’s based on the average trending rate of one guillemot per kilometre of beach per day in the Netherlands with 300km [186 miles] available. That’s 10,000 birds,” he told the BBC. A similar number would have been left in the sea, he added.
Although he is keeping an open mind, he points out that the birds began washing up at the time of the container spill. Bad weather can also affect a guillemot’s access to food, but Mr Leopold believes the problem would then not have been confined to the Dutch coast.
While the guillemots may have swallowed plastic pellets, a spill of paraffin or palm oil was perhaps more likely. The island of Terschelling, where much of the MSC Zoe debris washed up, has also seen paraffin appear on its beaches.
On Wednesday, Dutch authorities said that at least 345 containers had fallen off the ship, 54 more than first thought.