Several swans found dead or severely ill in Laajasalo, eastern Helsinki, are believed to be victims of lead poisoning by shot-pellet ingestion, says the Finnish Food Safety Authority (Evira).
"That's the strong suspicion at the moment, that it's a case of lead poisoning. This can be confirmed by measuring the lead content of their tissues, says researcher Minna Nylund of Evira's wild animal and waterfowl unit in Oulu. The tissue samples will be analysed in Helsinki.
Nylund suspects that the swans had ingested lead shot illegally used in waterfowl hunting, which had settled on the bed of the sea and other bodies of water.
"Swans ingest grit from the seabed to help digest their food, and these bits of lead shot are the right size, so they consume them by mistake," she explains.
The use of lead shot is banned in waterfowl hunting in Finland.
Four swans were found in Laajasalo last week. One was dead and the other three were in such poor condition that they were euthanised.
Another swan was found in weak condition on Friday. It was taken to Korkeasaari zoo's animal hospital.