Absence of Slugs and Snails


I have noticed a decline in the number of slugs and snails in my garden in Redditch. As these are common food items for birds and as I have done nothing to cause this, I was wondering if this is more widespread of just a local situation.

Basically I haven't seen a slug or snail in my garden in the last 18 months. I used to typically see 10 to 20 or more when the weather was damp.