“… the sound of a glass bottle being blown across its open top” or a deep, resonant “boom” as if from many miles away… the voice of Botaurus stellaris, the Eurasian Bittern.

I heard that first, at RSPB’s Minsmere reserve at the Suffolk coast, in the very early 1970s. I was out with a group of “Lady Birders” from Flatford Mill Field Studies Centre. I was not a Lady Birder – I didn’t even have a pair of binoculars. I was working as a kitchen help at Flatford in my gap year before college, and I had taken the chance of a free coach outing on my day off.

Confused by Redpolls, uncertain over shore birds, perplexed by the rareness of Bitterns – but yes, I had heard the strange echo from far away, and was told – by the stern and earnest leader – that I was very privileged to hear – from afar – this shy bird.

Yesterday, after an interval of forty-seven years and inland this time, again I recognised a bittern booming, way towards the east. And then a few minutes later, just as we were leaving the reserve, another, this time towards the west, at the other side of the reserve. Definitely a second male.

Each time, two or three repetitions, a few seconds apart. at the same deep, baritone, pitch. Otherworldly almost – voiced as if through a long mist. Ethereal.

My friend had discovered – last weekend with family guests to entertain – a wonderful new reedbed area, a continuing cooperation between the RSPB and Hanson UK at Ouse Fen, a vast site of gravel extraction. It is set to become the largest area of planted reeds in the UK. Part of a wetland corridor through the Cambridgeshire Fens. And really close to her home.

So yesterday she and I set off – her dog Echo obediently on a lead – under the lively wide sky of piling clouds. The reed heads were bronze, the lagoons ultramarine. Hawthorns and sycamores were showing new leaf.

We heard and saw a buzzard, and watched as a female kestrel stooped for prey. Close in, from a waterside thicket, we watched a Reed Bunting fly ut and away. But the “seen” Bird of the Day was a Marsh Harrier, elegant, leisured, making several passes across the water and reed. It was near enough for us to see the dark areas at its wing tips: it seemed comfortable with our proximity, and that was a sight of a lifetime.

Almost content with those sightings, we were returning through the kissing gate when the booming started – one, two – stopped. A minute later, a confirmation that we were not mistaken, at exactly the same pitch.

And in a path-side pool there was then a commotion as “dabchicks” – Little Grebes – postured and played in earnest, with a bubbling almost feisty accompaniment as the splattered across the the surface, one in pursuit of another.

Then we were delightedly walking back along the rutted roadway, between newly budding branches where warblers chanted loudly and intriguingly. Stopping to get better sightings of these smaller birds, their varied and rich songs teasing us. Being pleased I had bothered to wear my hearing aids today, so that skylarks had been almost raucous.

And being glad as yet again, this time from a different part of the reserve, the booming began again. Another bittern, holding his ground, boldening his proud bass baritone. “I am here, hear me.” Already the hoped-for flagship bird-of-the-future for this new reedbed is present and correct – they are present – and contributing presence to the biodiversity plan.