Through these last weeks of summer, the autumn migration has played out in the skies, though it goes largely unnoticed by most below. A trickle of an exodus began over the bank holiday with three dark specks, way, way up in the blue. Specks, yes, but you could see, from the wings curved like taut bows, that they were unmistakably swifts.

Hatched on northern ledges they had become citizens of heaven. They deviated on insect-chasing sallies in all directions, but were overall tracking south-west.

The swifts were almost lost over the horizon when three more materialised in the same spot as the first trio. And then, when those birds had nearly gone from sight, another cluster appeared, and then, when they too were at vanishing point, yet another.

For half an hour, until I was summoned back to my paint brush, I watched this loose but connected procession of travellers traversing the sky. I regretted afterwards that I had not stayed to see whether the chain stretched over tens or hundreds of miles.

House martins can be heard chattering while in flight. Photograph: FLPA/Alamy

Whenever waves of humidity roll in and the clouds bank up, the air is salted with the frenzied chatter of house martins. Most people must hear them, but no one looks up. Maybe it is just background noise.

I watched one of these pop-up flocks the other day, the birds cutting across each other against an ominous blue-black backdrop. All but two of the birds were purposeful in their “fast flap, glide” fly catching, the old and the young milling together in the currents.

There was an errant pair in their midst. House martins are noted for their antagonism towards rival birds close to the nest site, but it seemed these two had carried their dispute into the departure lounge. They broke from the crowd to engage in a fierce beak-to-tail chase, tracing loops, bows and chicanes, bodies flashing light-dark-light-dark as they turned.

A passive observer, I nevertheless felt the speed, exhilaration – and also pointlessness of the pursuit. Why waste so much energy instead of fuelling for the journey of their lives? It seemed that, for this pair, there was time enough to bicker.

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