Aredwing chases a blackbird through the drizzle, away from a group of rowans and over the hedge north with an emphatic “and don’t come back” cackle before veering off to resume guardianship. It will. During the cold snap, the redwing-rowanberry drama was muted, the ground bone-hard, every fruit frozen, the birds sitting it out. Now there’s a thaw, the redwing is resuming security patrols around trees with remaining rowanberries. Since they arrived from Scandinavia or Iceland some weeks ago, the redwings have been snaffling berries, but this group of mountain ash – rowan, rune, ran, roan, royne or, over the border, criafol – have been left to ripen. It’s a great year for fruit and seed and these trees, planted in recent years, are loaded with berries. Perhaps the birds find them particularly good when they’re frosted and this may be why this individual redwing has been going to such lengths to protect the crop until it peaks. Fiercely guarding the berries, from blackbirds particularly, not at all intimidated by jackdaws, this redwing must be exhausted but still shouts that scratchy shakshakshakshak, harries and dives to chase thieves away. What is going through that head? In the brain, “synaptic weight” refers to the amplitude or strength of influence the firing of one neuron has on another neuron, when a cell is close enough to another cell to excite it; this happens in the creation of memory and is the process of learning. The brains walking on grass, perching in trees, flying through the sky, all of them fizzing with firing neurons, have a kind of music of remembering, how this looks, how it feels, where it is, its synaptic weight. Redwings and humans learn through sensory processes, we can share memories. A frozen rowanberry has a crunch, an appley, cranberry-ish flavour, sweet but with an after-tang like cider vinegar; it turns spit orange. It has an intoxicating strength revealed through frost. Such learning is found at the end of a journey, when the days are thin, cold is sweet, before the long turn to the sun.