THE WORLD HAS gone mad. I have spent most of this week in the mad month of May beneath the mad May sun, and I have been moving from madness to madness. There was, for example, a curlew putting out an aerial version of the John Cleese Silly Walk. It was not flapping properly at all — instead, shivering its wings in a ridiculous way, and all the time, making a hysterical, piping: look at me, look at me!

Then a lapwing, rising up and diving headlong down again, turning itself into a paper dart, and all the time filling the air with a mad oboeing. After that, the butterfly flight, showing just how floppily a lapwing can fly when it really puts its mind to it: and then the wigwag flight, a wild side-to-side yawing.

When you see a bird or any creature acting in a way contrary to all reason, you don’t have to be Charles Darwin to work out the reason why. It’s sex. Sex and territory,which is very much the same thing. When a curlew does the Silly Fly, he is telling the world: I’m too sexy for my beak.

Even the meadow pipit gets silly. A meadow pipit is one of the nation’s most overlooked birds: small and self-effacing, the kind that is frequently termed LBJ, or little brown job. (Incidentally, Spanish birders have a similar terms: hijoputido, translating roughly as little bastard passerine.) But in the high spring, the meadow pipit takes leave of the ground and its senses, flies up high, shouts its name again and again to the surrounding countryside and comes down in a spectacular paraglide. I may be small and brown but my heart and my soul are large and filled with colour.

• AS YOU watch the whitethroat, you realise why young lads are such eejits. The whitethroat is a warbler, a member of the hijoputido, and it comes here to breed in thick hedges and brambles. You can hear him singing at this time of year, in a cracked, sore-throated fashion. When the sun shines, the blood flows hot and strong, and the strain of all this frenzied singing is more than its tiny body can bear, then the whitethroat flies from its perch and climbs above it, singing at the top of his voice: come and get me!

That’s an invitation no passing sparrowhawk will turn down. But that’s rather the point. He is showing the passing females and males of his species that he is brave and quick and agile, so much so that not even sparrowhawks seriously worry him. That song-flight tells any rival male that he is far too tough to tangle with and every passing female that this is the whitethroat for her.

It is an enthralling contradiction — that an apparently death-seeking activity is in fact the most life-affirming thing that a male whitethroat can do. And it is reflected in human behaviour, by the stupid driving from herberts in racy Fords, by the bluster and braggadocio of young males, by the danger-seeking — in sport, mountain-climbing, riding horses, and on and on — that some of us never grow out of. Not because we love death but because we love life. That’s what the whitethroat tells us.

• ASK MOST people how many birdsongs they know, and they will answer, none whatsoever. Perhaps you who read these words will think, yes, it’s all very well going on about whitethroat songs but I couldn’t recognise a single bird with my ears.

  But you know at least four. You will know the Hammer horror sound of the owl (the tawny owl’s to-whooo), the Desert Islands Discs call of the seagull (in fact, it’s a herring gull), and the quack of duck (actually female mallard). And you will know the sound that I heard and rejoiced at this week. Cuckoo!

Is there a bird whose voice is so much a part of his being as the cuckoo? Thinly spread, without nests or territories, the cuckoo must find its mate by the power of voice alone. That’s why the cuckoo’s call seems to dominate vast landscapes, fill wide valleys, wrap around hillsides. Cuckoo is not just the sound and the name, it is the core of the cuckoo’s nature. That’s why you don’t often see one: because they are always so far away, even though you can hear them so clearly. That’s the point.

But I did get a glimpse of one: flying low over the reedbed towards a stand of trees, looking dramatically like a sparrowhawk. And before long, if all goes well — at least for the cuckoo — some poor reed warbler will find itself nurturing a ravenous and murderous giant.

Nature is always marvellous: but it is only sometimes pretty.

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