Look Out

The problem of small animals, and small insects. As body size reduces, of course both the volume of the body and its 'skin' area decrease. But they don't decrease at the same rate. If you halve the diameter of the body, you might reduce the volume by eight times but the body surface area by only four times. As size reduces, it becomes harder and harder for the tiny body to compensate for the heat lost from its surface, especially in winter 

Bees address this by forming a cluster during cold conditions. They congregate together in the centre of the brood box: as far as possible, pressing their bodies together to make a much larger body mass, with a lower surface area per bee. Wrens do exactly the same thing. Though highly competitive in the breeding season, they form clusters on cold winter nights - typically in bird boxes, under roofs or in rock crevices (which gives them their Latin name Troglodytes). I have read about it; I have had it graphically described to me by an old countryman who has seen it, but I've never seen a wren cluster with my own eyes

Two surprising facts about wrens: 

They are not Britain's smallest bird; that honour goes to the goldcrest

They are the commonest breeding bird in Britain. I was very surprised by this, but the RSPB and other sources are emphatic. They are so clever at staying concealed - and being small helps - that seeing them, especially close enough for a phone picture, remains rare enough to cause a frisson of excitement

Because they appear more frequently as the weather warms, they are traditional harbingers of spring - which, in Celtic tradition, begins with tomorrow's celebration of Imbolc. We have been alerted. Have a good one