I have lived in the same house with a small suburban garden for 17 years. When I came the garden was mainly lawn and there were lots of snails, apple green, orange, and cream and brown striped. We occasionally saw a thrush. We have never used slug pellets. Now the garden has some small shrubs around the edge and there are very few snails. I have not seen a thrush for a long time and do not recall noticing one last summer. Is this change in the snail population something general or only a local phenomenon?