Mx Autumn 
I put fat balls out on Monday and normally they are gone by Wednesday but appear to have been untouched. Do birds not eat them in the summer/autumn or has something weird happened to my local bird population?
vga256@carbontwelve yep. they generally start eating fat in the late fall and winter when they have a hard time staying warm and food reserves are low.
(and besides: right now is caching season - fat stores poorly!)