Cranes, cuckoo and more thrilling encounters at Wicken Fen

Our swifts arrived late this year. I usually spot the first individuals around May 4 or 5, but this year I had to wait until May 9, and they seemed fewer in number. And still no house martins spotted. Is it the general decline in insects, or the earlier rather dull weather?

At Wicken Fen, however, the migrants were much in evidence. Willow warblers sang from birch and sallow thickets and reed warblers from the reedbeds, where they kept themselves well hidden.

Blackcaps too were in full voice, and here and there in the thicker damp scrub Cetti’s warblers announced themselves with sudden loud staccato phrases.

One song sounded different — more rapid and less varied than the blackcap, but still musical and lacking the high-pitched final flourish. My guess was garden warbler, soon confirmed by sight. I think this species is misnamed as I have never seen it in a garden, unlike blackcaps, which are now regular garden birds.

From a distant copse came the classic two-tone call of a cuckoo, a welcome herald of early summer and always uplifting to hear. Wicken is one of the best sites to see (or usually just hear) cuckoos as the big population of reed warblers there gives them a good choice of hosts. We heard four cuckoos calling, probably different individual birds.

Late spring and early summer flowers were much in evidence - broad, flat white clusters on the elder bushes, feathery inflorescences on tall groups of hemlock, creamy-white drooping flowers of comfrey, and pink or white flowers on wild roses.

At one point we paused to gaze out over a field dominated by grasses, rushes and sedges, fringed by trees, scrub and reedbeds. A low, grey shape in the middle distance caught my eye. Checking with binoculars I expected to see a rabbit or hare or perhaps a small deer. To my surprise and delight a crane reared its head and gazed nervously round, and soon a second head appeared. Both birds, clearly a pair, moved slowly along, rearing up every few yards to check their surroundings.

We kept our distance so as not to disturb these rare birds and eventually noticed a russet-coloured chick trotting along to keep pace with its parents.

Later, I heard a strange bugling call from overhead. A second pair of cranes circled above us and then headed out over the fen.

Cranes are large birds, standing over a metre tall and with a wingspan of more than two metres, but are secretive when nesting.

They have been extinct in Britain since the 16th century until only quite recently, having long suffered from hunting and habitat loss. Starting with a pair in Norfolk in the early 1980s, they have steadily recolonised, notably in the fens. Since 2019, one or two pairs have nested at Wicken Fen, and they also breed at the RSPB reserve of Lakenheath Fen.

Marsh harriers and buzzards circled in the distance, and I had a sudden tantalising view of a harrier that looked quite different. It was almost entirely pale grey, so I immediately thought it must be a male hen harrier. Hen harriers are regular here in winter roosts, but this was surely too late. Could it have been another special bird, scarcer even than the cranes, a Montagu’s harrier, one of the country’s rarest breeding birds?

I enquired, but nobody else seemed to have seen it, and I cannot be sure. I am still replaying the episode in my mind, trying to tease out the details, but the element of doubt remains, though I can still sense the thrill of the encounter.

• Martin Walters is a Cambridge-based nature writer and conservationist.