Michael McCarthy: Winter of '63 battered evolution's defences

Nature Notebook: It was suggested that half the birds in Britain died

Evolution tests species to destruction. Evolution selects ruthlessly for fitness to survive, whether it be in behaviour, or in physical attributes, so when we see any animal species in front of us, we can be more or less certain that, after thousands of years of testing, as it were, it can handle anything the natural world can throw at it, unless the circumstances in which it evolved have radically changed (for example, by the advent of men with guns, or pollution, or pesticides.)

Take wading birds, such as the curlew, or the redshank, or the ringed plover. We see them in wild landscapes, often at the edge of the sea, where there is no shelter; in winter, the wet and the cold are their constant companions, yet they are untroubled; they have evolved to survive perfectly well in such conditions. The idea that a wader might succumb to the cold of the sea is entirely counter-intuitive; otherwise the winter shore would be littered annually with feathered corpses, would it not? Yet once I saw such a thing, and it made a lasting impression on me.

It was January 1963, in the longest, hardest, coldest winter of the 20th century, when I was a slip of a lad and had just started birdwatching. I was walking along the seashore at Hoylake, on the Wirral, and to my astonishment the sea was full of ice, crushed ice from the action of the waves, something I have never seen since; and floating in the ice was a dark object. I fished it out; it was an oystercatcher (pictured), one of the handsomest of our waders. I gazed in awe at the perfect black and white plumage and the brilliant orange bill, and I saw that there was no mark of injury on it and I realised instinctively that I was witnessing something very unusual. I suppose then I would just have said, I found an oystercatcher killed by the cold. Now, with perhaps a little more knowledge, I am able to define what was so unusual more precisely: I found a wild creature, which had been overcome, in the natural world, by something more than almighty evolution had equipped it for.

A colossal mortality

Looking back, that was one measure of just how extraordinary the winter of 1963 really was, and it is the current long freeze, or course, which is prompting comparisons with it. It was suggested that half the birds in Britain died in '63; such a toll is probably unlikely in 2010 unless there is no respite for another six weeks, but there will still be a colossal mortality, especially of the very small birds such as wrens and goldcrests. Evolution will not save them, either.