Swifts, swallows, house martins and sand martins flash by at astonishing speed below me as I stand on the Thames towpath at Kingston.

From my elevated vantage point I look down on the super streamlined summer visitors and can easily distinguish the diagnostic features of each species.

The glossy royal blue sheen and long tails of the swallows, the plain sooty brown upper surfaces of the swifts, the blue-black house martins with prominent white rumps and the overall lighter warm browns of the more dumpy sand martins.

All the birds are skimming the surface, snapping up a bumper mayfly hatch, for after all, with the exception of the swifts, the others may have up to three broods during the short summer and need to provide a constant food supply to growing fledglings.

The mayflies have spent two years as nymphs living on the river bed but it is now time for them to float to the surface and begin their phemeral lifespan of barely a day. However, for many of them their new airborne lives as winged adults are cut short in seconds as they sit on the surface, dry their wings and prepare to flutter weakly to the riverbank.

The birds fly low and fast, zig-zagging, using exceptional eyesight to scoop up insects on the surface or taking off.

Any mayflies that manage to reach safety will sit on vegetation, shed their skins once more and join a mating swarm rising and falling over the riverbank. There, they pair up, lay eggs and die.