Slugs. The suggested remedy is to put sand around the top and bottoms of Lilly bulbs to aid drainage and to stop slugs eating emerging leaves. Slug pellets would be a better but try the sand method and cone it up so to get a good stem length.

Thanks Kildermorie - are slug pellets harmful to the birds...if so I'll go down the sand route otherwise off to the garden centre to get those pellets before the lilies are completely gone!

You can buy slug preventatives which are not harmful to other creatures. Some of the ones sold are deadly to anything which eats the dying molluscs and some are really very poisonous to cats and dogs.