Yom Kippur is coming up on Monday. In Leviticus 16, the real action of the ancient ritual concerned two goats. One goat was slaughtered and the blood cleansed the sanctuary. The other, the "scapegoat" or the goat "for Azazel," had the people's sins passed upon it and it was driven into the wilderness (evidently where Azazel was).
In Brooklyn on Monday Hasidic Jews will sacrifice a chicken in the "kapparot." The idea is that sins are transferred to the bird and then disappear at its death. I don't know much about this ritual, its origins, its explanations, and its developments. But it sounds like the two goats from the ancient ritual combined together into a single chicken.
Interestingly, it seems that this ritual contravenes rabbinic rulings on proper slaughter of animals.