IT IS MY first nightingale of the year, and a coloratura bird into the bargain. It has a clipped, Latin style, full of deft phrases which are turned this way and that and drawn out into short, fading tremolos. As the moon rises, changing from hazy orange to platinum white, the singing becomes more assured. The sound is astonishingly pure and penetrating, broken with teasing, theatrical silences. I realise I am rooted to the spot, standing in the middle of the lane and barely noticing the cars edging past.

No other birdsong can match these outpourings under the May full moon. Even by nightingale standards they seem more eloquent and passionate than at any other time of the spring. Perhaps this is just a flight of fancy on my part, a touch of moonshine. But it is a critical moment in the birds’ year. Ever since early April nightingales have been migrating back to Europe from their wintering quarters in tropical Africa, running the gauntlet of bird catchers and Mediterranean storms. The advance guard are almost all male birds, and since their arrival they will have been scouting out nesting territories in woodland thickets and river valleys. The females follow a week or so later, choosing warm, clear nights for migration if possible. These nights in early May mark the crescendo of the nightingales’ courtship. Territories are settled, female birds are on the move and choosing mates, and the last waves of new arrivals are winging in. No wonder the males’ songs seem so intense: they are serenades to tempt the females down from the sky.

This spring of all springs, I hadn’t expected to be listening to nightingales in the austere landscape of East Anglia. It was meant to be Portugal, with the woman in whose company I had trailed the birds across northern Europe all the previous spring. Lily and I had planned to share our first birds of the year under the almond blossom in Alentejo. But the relationship faltered (plenty of singing but no shared territory) and we went our separate ways.

The spring after we parted was, as any good romantic is entitled to expect, dismal and pinching. Snow fell at Easter. The summer migrants were a whole month late. When the swifts finally arrived in early May – a thin, defiant arrow of birds careering in from the east as I was coming home from the shops – I was so relieved to see them that I drove the car into the kerb. But they proved to be the best of omens, and within two days England was suffused by exquisite, balmy weather. Having no stomach for moping alone by the Mediterranean, I sped to East Anglia, where I had first been bewitched by nightingales twenty years before.

THERE IS A lull in the singing, a huge emphatic silence that seems to be part of the performance. It is about ten o’clock and the moon is almost at its height. By Suffolk standards I am on top of the world. Below me, Arger Fen arches like a whaleback across the whole span of the southern horizon. Everywhere, dead elm stumps rear in silhouette amongst the scrub. The light is extraordinary – luminous, dusty, giving every pale surface the lustre of mother-of-pearl. Mounds of cow parsley and scythed grass glow in the moonbeams like suspended balls of mist. By the side of the lane I catch the scents of broom and bluebells, a blend of coconut and honey, the exotic and homely, that has something of the ripened quality of the song itself.

He is louder and more extravagant now, and seems to be rehearsing the whole nightingale repertoire. He sings a stylish four-note phrase, then repeats it in a minor key. He slides into a bubbling tremolo on a single note and holds it for more than ten seconds. How does he breathe? I cannot believe he is not consciously improvising. I want to clap – and with barely credible timing, a shooting star arcs over the bush in which he is singing.

I am edging closer without realising it and am now no more than ten feet away. Nothing stops the flow of notes. They fill the air, they seem to be solid, to be doing odd things to the light. I am half-aware that my peripheral vision is closing down, and that I am riveted to the bush by this tunnel of intense sound … But the effort breaks the spell and I start to walk back to the car. The bird begins to recede and I am left, puzzling again over how another species, supposedly going about the routine business of defining its territory, can have such an extraordinary effect on one’s senses and emotions.

Whistling in the Dark: In Pursuit of the Nightingale by Richard Mabey with illustrations by Georgina Warne is published privately. Limited-edition copies are available for £50.00, incl. p&p, from: Mazzard, Snow Street, Roydon, Diss, Norfolk IP22 5SB.

Richard Mabey is the author of Food for Free, Flora Britannica and Nature Cure.