Culturally, if not taxonomically, the sheathbill is the pigeon of the Antarctic. So lowly is its status that some folks call them shit chickens.
Like chickens, and unique among Antarctic birds, their feet are not webbed. They are also chicken (free-range, anyway)-like in size. They are common and they are scavengers.
Given a chance they'll feast on the eggs of penguins, terns or petrels. In a pinch, they'll gorge on feces (no cracks about reporters being the sheathbills of the human world).