Cold snap

Here are ten numbers to go with this week’s cold snap.

 Zero: officially speaking, a frost day is any day in which the minimum temperature falls below 0°C.

Forty four: in 2023 there were 44 frost days recorded in the UK, only six of them during November. The Met Office is reluctant to say whether or not this cold snap might last longer than six days.

Thirteen: the number of days by which this decade’s average first frost is later than it was a century ago. This number is rising slowly but inexorably, a frightening reflection of our warming planet.

Five: 5°C is the temperature at which grass stops growing.

Eight: we are in Zone 8 of the frost map published by Plantmaps, which predicts that the reserve’s last frost will occur in the final ten days of March.

Twenty: in order to stretch resources as far as possible during the winter, a common shrew shrinks by up to 20%; its spine shortens, cartilage is re-absorbed and even the brain and skull get smaller. Moles use the same tactic, shrinking by 11%.

Five hundred: the weight in grams that a hedgehog must achieve if it is to survive hibernation. Late-born hoglets don’t usually make it through their first winter without help.

Seventy: the percentage increase (70%) in the weight of a house sparrow’s plumage as it prepares for winter. Most of the additional weight comes from a dense layer of down close to the bird’s skin.

Six: the percentage of its body weight a great tit can lose overnight in cold weather. Small birds need shelter in a cold snap so leave your bird boxes out for the winter, cleaned and with a handful of dried grass or dead leaves in the bottom.

Sixty five: approximately 65% of blue tits die in their first winter.

Go carefully in this treacherous weather; don’t become a cold snap statistic.