Crow Feather

I picked this up during my visit to Vane Farm RSPB reserve in Fife. I like crows, especially rooks. During our trip up north earlier this month we saw a crow trap used by gamekeepers. There were three crows inside, in a state of panic and distress, and the temptation to free them was almost overwhelming. I know that "country folk" say that crows are a pest but I'd like to know how much scientific evidence there is to justify this sort of cruelty.