Monday morning, the yard covered with a thick blanket of snow, but hints of global warming — six male robins and some starlings visited the privet and sniped the dark berries one by one. They were at it yesterday as well. The berries looked black, but when digested and defecated, they left deep purple stains in the snow. Privet berries must be emergency rations for berry-eating robins, which never feed on seed or suet.