A Cuckoo Calling In The Distance At Wicken Fen

It's very faint and it only lasts eight seconds but it's the sound of summer at the fabulous National Trust national nature reserve in Cambridgeshire.

And if that's the sound then the carpets of marsh orchids among the reeds are the unmistakeable sight at this time of year. We strolled round the two-and-quarter-mile Nature Trail of wide droves and lush green paths that circle the undrained Sedge Fen. The warblers were out in force but the blustery winds meant the reserve's famous dragonflies were keeping a low profile.

First stop, after a sausage sandwich and a refreshing bottle of Boathouse Bitter from the City of Cambridge Brewery in the cafe, was the excellent visitor centre. One of the wardens was happily holding a very calm Sparrowhawk. With eyes and a bill like that no wonder it's feared throughout the warbler world. As soon as it was released it was straight back into hunter mode.

An insect hunter had also made itself at home in one of the other man-made structures. This Swallow seemed completely unperturbed by the stream of visitors clattering in and out of the Roger Clarke hide, repeatedly dodging the binoculars and telescopes to fly to and from its nest in one of the dark corners. There was no sight nor sound of chicks so presumably she's waiting for eggs to hatch.

Among the other highlights of the walk was this magnificent caterpillar found on the boardwalk by low-level Grace. We had no idea what it was at the time but it didn't take long for Professor Google to reveal that it's the larva of the Drinker Moth - which UK Moths say is a fairly common species in southern England and will take to the wing in July and August.

We'll look out for it.