SO, that's just about it. Here we are in July and I haven't heard a cuckoo.

How does that old rhyme go?

The cuckoo comes in April.

He sings his song in May.

In the middle of June

He changes tune,

And in July he flies away.

Very little time left, then, to hear the timeless herald of summer. Never before has the bird not accompanied my own late springs and early summers. My grandfather listened keenly for the bird at the country brickyard where I was brought up, and I picked up the habit from him. In recent years, the cuckoo's "two-fold shout", as Wordsworth characterised it, seems to have been getting rarer. In several places where I used to hear it, and others where I would have expected to hear it, it has been absent. But my home patch, the farming country bordering the Cleveland Hills near Stokesley, seemed to remain a cuckoo stronghold.

So evocative of the meadows, woods and hedgerows that form the quintessential English landscape, the call came unfailing in about mid-May. Soon, the early morning stillness in particular almost echoed with cuckoo calls. At least two male cuckoos seemed to occupy adjoining territories, one in open fields and scattered woodland towards the hills, the other centred on a disused railway line thick with hawthorn and briar.

Last year, however, I heard only two faint calls. And this year - silence. Nor have I heard the cuckoo in several other seemingly ideal locations I have visited in the past month or so - Sinnington Woods near Kirkbymoorside, Arden and Rievaulx in upper Ryedale, Rosedale, Farndale, Glaisdale, Wensleydale, Fountains Abbey, Borrowdale and the Windermere fells. Yes, I try to get around our glorious North Country.

People from some of these places assure me they have heard the cuckoo, and no doubt others have heard it elsewhere. But for an avid cuckoo listener to draw a blank across such a wide canvas still strikes me as a phenomenon worth airing. What might my first, sad, cuckoo-less spring signify?

Of course, the cuckoo has its critics because of its disagreeable habit of evicting the chicks of its adopted parents. But a countryside in good heart, a thriving, well-balanced countryside, allows the full range of wildlife to flourish.

If the cuckoo population is declining, alarm bells should ring because the cuckoo's plight might mirror a similar decline among its host species.

Of the bird's three favourites - dunnock (hedge sparrow), reed warbler and meadow pipit - the dunnock is almost certainly the first choice in mixed farmland. Though abundant in gardens, perhaps it is now struggling in the open countryside, which is still the cuckoo's domain. Could it be that the reluctance of the shy cuckoo to follow its main host into gardens, now a haven for many hard-pressed farmland birds, is threatening its future?

Alternatively, the problem could lie in the bird's winter quarters in Africa. And the charity Butterfly Conservation has pinpointed a shortage of tiger moth caterpillars, eaten exclusively by the cuckoo, as a probable reason for the bird's acknowledged decline in southern Britain. Harried and persecuted, the much-maligned magpie is almost certainly not to blame.

Addressing the elusive cuckoo, Wordsworth asked: "Shall I call the Bird, or but a wandering Voice?" He recalled that in his boyhood "to seek thee did I often rove through wood and on the green; And thou wert still a hope, a love, still longed for, never seen." And he concluded: "Even yet thou art to me no bird but an invisible thing, a voice, a mystery."

Luckier than Wordsworth, on the day my son was born, 40 years ago next month, I saw a young cuckoo perched on a fence at my parents' isolated home on the Eston Hills. And two summers ago two cuckoos - a pair, perhaps, or competing males - flew just feet above where my wife and I sat on our garden seat. One of the birds cuckooed loudly as it passed overhead.

At least I think it cuckooed. Looking back I can't be sure the call wasn't "Adieu".