Through a naturalist’s eyes
"I returned from Antarctic regions in early January to find myself in the coldest spell for four decades. In due course, we shall learn what effects this has had on wildlife populations, but I remember the Wren as one species being particularly head-hit in the winter of 1962/63. Its population dropped from seven million to one million pairs. The small size of the Wren makes it very vulnerable to low temperatures, but survival on cold nights must presumably be enhanced by its habit of communal roosting."