The Day After Tomorrow - Chopper's Freezing

Never known it so cold without snow. -10 when I got in the car this morning. Apparently likely to snow over the weekend. Watched a couple of roe deer at Green Park last night - how do they survive such low temperatures? It is incredible. Also observed a roost of goldfinches that numbered at least one hundred congregate in a laurel bush. They were very animated and then then all of a sudden went completely quiet - perhaps to avoid raising the awareness of nocturnal predators. I wonder if they roost alongside eachother ot share/conserve heat or keep a respectful distance like starlings. Might invest in an infra-red camera and find out....