The hunting forays of about 30 swallows lassoed an area of swaying grasses at Lightwood, but I noticed that several small rowans operated as their rest camp between sorties. The birds further enveloped those trees in their delicious song, producing a collective music that has the same structure and soporific impact as the sounds of water dissolving stone very, very slowly. It was entrancing. In the soft post-six-o’clock sunlight, swallows shone lustrous blue, but no design by Lalique could match the gem-like quality to the finish in their plumage: the nine or 10 pearl spots to the tail, the widening lozenge of rose quartz at their throats. They were mostly young birds, perhaps three to four weeks out of the nest, with the telltale pale gapes of nestlings, but even these creases of citrine somehow added to their overall aesthetic effect. Occasionally, at the dash past of a sparrowhawk or the float overhead of several buzzards, the swallows flew out in heated pockets of fiseew alarm notes. It is sometimes hard to recall that this most beautiful and beautiful-sounding of summer songbirds – and surely no other combines all attractions – is itself a remarkable predator. Photography revealed it best: images of low-flying birds, just at grass height, so fluid, so elliptical in profile that they resembled flying saucers. Few of my 1,600 frames were in focus, but one blurred sequence shows a swallow pausing mid-assault, twisting backwards, the wings flailing to stall the line of attack, so that the body is almost vertical with beak reaching backwards – overhead – as if the whole manoeuvre might crash​-land the bird on its back. But no. The fly was taken. You can just make it out, pincered in that tweezer of a beak. We should recall, however, that flies, with aerial capabilities of more than 100 wingbeats per second, are in a permanent arms race with the blue birds. Evolution is unfolding even now. Prey and predator, in glittering evasion or superb pursuit, are moving on towards greater, higher attainments. The world of nature is becoming more perfect (if more profoundly troubling) even as we watch.