Nature writer SIMON BARNES looks forward to Nature's stirrings for a new season.

It can be a tease, that nature. One day I walking in snow so thick I could only see the black bits of the magpies – bleak midwinter, earth hard as iron, water like a stone, you know the routine. Two days later it was spring, even though we're still in the middle of January. No doubt it'll be winter again tomorrow or the next day.

The air was so still the smoke from the Cantley beet sugar works was rising almost vertically. The sun was shining with that eager brightness you only get very early in the year, when it's a mild shock to see a shadow on the ground. There was even a hint of warmth in the day.

The wild world responds to such drastic alterations loudly and vividly. I stood out there in the sun for a couple of hours or more, for the farrier was shoeing the horses and I was needed to do my bit. The merry tonk of hammer on anvil and shoe and nail mingled with the spring-time cries of the birds: one of those eternal Norfolk moments. You know the routine.

There was a dunnock singing his head off in a little tangle of scrub. These are drab and secretive little birds that spend a lifetime being overlooked, at least by most humans. They are happy on the fringes of human life and are always enthusiastic members of the early-spring movement.

Their song doesn't stand comparison with the luscious stuff that will be coming our way later in the year, but that day it was a thing of special beauty. That's because it's happening now. The cock-bird was singing out a cheerful, rather flat jumble of notes, apparently thrown together in hasty fashion and belted out in a will-this-do kind of spirit.

He was joined, more or les inevitably, by a great tit. These birds are on a hair-trigger alert this time of year: any hint of sun or warmth – and sometimes without much of either – they will belt out two notes again and again: teacher-teacher-teacher, or as some hear it, the sound of a squeaky pump.

After that I heard a blue tit, softer and more restrained, less downright, chucking out a handful of notes almost despite himself, as if he didn't really want to do it. Birdsong is back. It will rise to a peak in early May and then very gradually fade out again. There'll be plenty of stops and starts on the way, but right now, on fine days, the air is full of the sound of – well, sex, actually.

Also territory, song being a keep-off to rival males as well as a come-on to gorgeous females. It's also – eventually – about the feeding resources for a nest-full of nestlings. Whatever way you hear it though, every song from every bird is the song of life.

There were two buzzards high up, flying in close formation and performing complex little bits of aerobatics: more interested in each other than in the next meal, at least for the moment. And then the crash and bark of heron, one flying past and then another. Of course, there was also a pair of collared doves in a tight two-shot, birds always happy to be half of a pair. When birdwatching becomes binary rather than singular, spring is beginning.

And then two more birds together: just silhouettes and at too great a distance for naked-eye identification – I had horses to hold, remember – but I think they were great tits. One was chasing another with great enthusiasm, in a manner that reminded me of a French-farce spoof called Chase Me Down Farndale Avenue S'il Vous Plait.

Was this a bit of male and female interaction? Or was it one male chasing another? Was it aggression or attraction? Sex or a punch-up? Was it about joining up or keeping apart? These things can be impossible to distinguish but presumably the great tits (if that's what they were) knew what they were about.

Watching the arriving spring is like sitting on a beach watching the tide come in: there seem to be at least as many retreats as advances, there are times when there seems to be no progress but all the same and all the time, the tendency is remorselessly forward. Listen out, then: for the tide of spring – the tide of life is rising.