A few years ago, Bookham Common in Surrey, very near where I grew up, had 16 singing males; last year (I have since discovered, from speaking on the phone to Ian the warden) there was only one. There's one again this year, singing within hearing distance of Ian's living room; "I'll have to get double glazing, it drowns out the TV!" he said.
I've been going there as the sun sets and circumnavigating the cottage, but I haven't heard it yet: only the cacophony of other birds that forms the evening chorus, the distant roar of the M25 and once some local lads playing music and drinking around a parked car. A birder I ran into had had no success either, while the local horse riders and dog-walkers mostly looked at me blankly, although "We get them on the golf course!" one did tell me. "Oh yes, flying overhead and singing so loudly. Up they go, so high..."
He meant skylarks, of course.
Ian the warden told me that at another Surrey site called Capel, where a retired couple have bought a wood and are managing it for wildlife, numbers have been going up, so my husband and I took the dog there on the Bank Holiday weekend; there were bluebells in abundance, and at one point we thought we heard what could have been that 'jug-jug-jug-jug' quite distantly – but I don't feel sure enough to say it was a nightingale for certain.
Bookham has yielded another treasure, though: a cuckoo, calling loudly for several minutes not long after I got off the train. It's been years since I heard one, and that was up in Cumbria; before that, in Dorset, five or six years ago. I don't think I've heard one in the Home Counties since I was a child.
As I turned to leave that night, disappointed not to have heard a nightingale but buoyed up by the unexpected cuckoo, a tawny owl shivered its note from a dim thicket. The strident song thrushes, dunnocks, blackbirds, wrens and warblers quieted one by one as I walked back to the station, night falling around me, the Common guarding its secrets for another time.