Squirrels love them and they distract them from the birdfood!
Of course the squirrels absolutely love this. When they see or hear me in the house they tap on the garden door and beg me to throw them a walnut. I have done many experiments with various types of nuts and found out that they always prefer nuts in shells and prefer walnuts to all others. Preference seems to be 1: walnuts 2: hazel nuts. Least liked are peanuts.