Evergreen hedge for a cold garden

Hi, I am looking for a hardy evergreen hedge, that will take temperatures down to -20C and will not dieback or go brown. I would like the hedge to form a windbreak and to provide winter shelter for birds. The site for the hedge is south facing, but partially shaded by tall deciduous trees, and the back of the hedge will be north facing and fully shaded by the trees. The soil is stoney clay, the ideal height for the hedge would be 15-20 ft, but it does not matter if it eventually got taller, and it must not be poisonous to livestock. I know that Holly grows well here, but I already have plenty of this and would like to try something different, Any ideas?