flack

They provide a useful service, said Flack.

There are huge clusters of organic waste they can feed on, said Flack.

The birds can easily eat pieces of plastic or rubber hands and they can die, said Flack.

Flack said it was too early to know whether the benefits of plentiful food outweighed the risks of feeding on landfills.

Andrea Flack of the Max Planck Institute found that birds following traditional migration routes were more likely to die than German storks that flew only as far as northern Morocco, and spent the winter there on rubbish dumps.

"They provide a useful service," said Flack.

"The birds can easily eat pieces of plastic or rubber hands and they can die, " said Flack.