Stories of Magic: Enchickening the Spirits

A long-haired Icelandic gentleman in tight plaid pants was telling me about his travels, and what he's seen of various local practices for curing illness by sacrificing chickens, and how he believes that witch doctors and shamans are right in buying off evil disease-causing spirits with chicken deaths.  While chickens are a reasonable enough currency being, as they are, ubiquitous, affordable, and easy to kill, it does beg the question of what the spirits do with dead chickens.  I'm assuming a nice spiritual cordon bleu is out of the question here.