That should be ok. Just keep it mixed up as best you can! I feed mine whatever I can get hold of. That generally means a lot of rabbit in the winter, and mostly pigeons in the summer, but I've always got my eyes open. When I go beating for local shoots, I'll take anything off their hands that isn't given away, or doesnt go to the game dealer- there's always the odd pheasant that's been shot from about 6 inches away, and is no good to eat! I take squirrels with the airgun whenever I can, pick up fresh road kill- songbirds, game birds, deer, rabbits whatever.
Liver is ok for them, just