Red squirrels – like their grey relatives – don’t hibernate, though they’re less active in harsh weather. These are tough animals-you can see them foraging even when snow is falling thick and fast. They also give birth well before winter loosens its grip. The first kittens of the year usually arrive in February or March, safe inside their mother’s drey. From below, you might mistake a red squirrel drey for the nest of a magpie or crow. But instead of being an open platform, the drey is broadly spherical with a domed, rain-shedding roof.

The external structure is a skilfully constructed scaffold of sticks, woven with thinner twigs, packed with leaves to keep out wind and rain. Breeding dreys are about 30cm across and typically close to the trunk, to provide stability in strong winds. They are luxuriously padded inside with soft material such as moss, lichen, animal hair and grass, and maybe refurbished and reused several years in a row. Repairs tend to be made with fine twigs woven in to the existing structure.

Litter sizes vary from two to six, with three or four the norm. The kittens are naked at first and heavily reliant on shared body heat and the drey’s thick insulation. In the early days the mother spends most of her time inside, emerging only briefly to feed or drive away intruders. Males play no part in rearing young. After three weeks the young develop fur, and by seven weeks they are ready to begin exploring the outside world. Often the mother will move out after her litter is weaned at about 10 weeks, leaving the young to decide for themselves when to leave home. Dreys are also used for shelter. Red squirrels are not territorial – adults occupy home ranges that overlap with those of their neighbours. In winter they frequently share resting dreys – even males that spend the daylight hours in fierce competition for the same female have been known to cosy up come nightfall as temperatures plummet.