I went birding this week: I ended up dragoning. I took a stroll around the RSPB's lovely North Warren nature reserve near Aldeburgh and - well, I didn't expect to see much, in terms of birds, tell you the truth, a little early for winter, a little late for summer. But it's never a bad idea to take a nice walk in a nice place, so off I went.

And the place was alive with dragonflies. I don't mean a few dozen: I mean hundreds and hundreds and hundreds. Every step I walked, there were dragonflies in sight: sometimes clouds of them rose up before me. At one stage I saw a dozen perched on the rail of a footbridge: lurking, ready to dart at any luckless passing fly.

There were common darters, and ruddy darters and a few migrant hawkers as well. But it was not the task of diagnosing the species that engrossed me: it was the spectacle of colossal numbers, thousand of animals all simultaneously revelling in the gift of a sunny day at the end of a dismal summer. The dramatic display was a result of wonderful timing: they had all emerged from the waters at a time when the weather was not too killingly dismal.

There is a public footpath that runs across the reserve, a lapsed railway line, a sort of roofless tunnel of vegetation. Butterflies thronged it: small and large whites, a comma, and again and again, splendid groups of speckled woods in cappuccino colours. The sun had brought them to life as well: almost as if all these insects were directly created by the sun (which I suppose we all are, in the long view).

Is a dragonfly really a dragonfly? Or is it, in fact, a nymph? All its life is, you might say, a preparation for the couple of months it will live as the finished flying animal. But it spends far longer as a nymph than it does as a fly: up to four years, in some species.

Versatile things, one of the most dramatic bits of metamorphosis you can find: first they are submarine predators, stalking the bottoms of watery places and scoffing all they can find: and then, at last, they rise up for its few brief weeks in the sun - where they operate as aerial predators, flying four-winged like Sopwith Camels, eating what they can, and when the moment is right, they will mate on the wing, stuck together, one in front and one behind like a flying tandem, chugging along the hedgelines and the waterways in eight-winged ecstasy.

Water works

Water. That's the key to it. The sight of a dragonfly means that water must be good. Those long nymphal years cannot be lived without clean, unpolluted water. A dragonfly nymph is a predator: and it is a fundamental rule that the predator is the most vulnerable creature in any ecosystem.

If the waters are producing dragonflies, they must contain great numbers of other creatures as well. When you see a dragonfly, you can cheer for more than the beast itself: you can also cheer for everything else that you can't see - for the fact that you are walking in a place that is properly alive.

Water quality is one of the key issues in the conservation of practically everything. It's the ancient equation: water plus sun equals life. But you have to look after your water if it is to work. Dragonflies tell you that something is right: dragonflies in these colossal, almost absurd numbers, tell you that at North Warren the waters are as wild as water can get.

Happy hobby

So I sat for a bit, and sitting is always a good way of seeing wildlife, and a female marsh harrier made a long, stately pass across the reedbed; odd to think that the reeds weren't there when I first visited the place 18 years ago. This place is a triumph of management. So I carried on with my sit, and then found myself performing the classic birder's double-take.

A swift! Then two pieces of information came charging in on top of this impetuous diagnosis - and yes, I know, those of you who fancy yourselves birders are with me already. Because this was too big to be a swift, wasn't it? And besides, the swifts are halfway to Africa already: long since left these shores.

It was a hobby, of course, a long-winged falcon that has the knack of thrilling wherever it goes. And its favourite food is dragonflies, so it hadn't picked a bad day to work North Warren; two pairs nested here this year.

In some ways, it's a contradiction: to spend most of the day revelling in dragonflies and then to end up revelling in something that kills them. But it didn't feel like a contradiction: it just felt like life, rolling out before me in endless forms most beautiful on a day when the sun had some real warmth in it. I walked on: to sample a pint of life from the Dolphin in Thorpeness, along with a life butty.

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