Scarcely a day of this blog has gone by without the Swift winning best supporting actor. Today it finally gets lead billing.

I could watch swifts all day, every day, and my notes from the week mention them more often than any other bird. But swifts love a windy day, and today was undoubtedly their moment to shine.

We’ve been lucky this year at the reservoirs. We had the earliest record of a swift in London on 13th April; usually they only arrive towards the end of the month. Since then their numbers have slowly grown at what must be a popular feeding spot for swifts across East London. The past few days have seen numbers estimated at 1,000 or more, and it is breathtaking.

Quite, quite breathtaking.

The wall of wind almost stopped me in my tracks as I cycled along Forest Road, but swifts, their scimitar wings pumping frenziedly like wind-up toys, powered past me before tilting, locking their wings and allowing the wind to slingshot them to one side or the other.

When I was a teenager I very briefly took up sailing. A family we grew up around were sailing enthusiasts, and their son — a championship winning solo dinghy sailor — needed a crew member to move up to the two person mirror series.

I was never bold enough to be a first-rate sailor, or middle-class enough to fit in, so I only lasted one season. But over that summer I felt an exhiliration I don’t think I’ve experienced since when trimming the foresail to the perfect angle, leaning back and watching the water zip by millimeters from the gunwale, the sail’s trailing edge pulsating in the wind.

For me, When that happened it was through chance rather than skill. Another failing of mine as a seaman was a poor intuitive grasp of the physics. Teenage sailors may not study fluid dynamics, but many could still sense the gusts, lulls and eddies around them, and glide not on the water, but through the wind; the water and the boat incidental to their soaring flight around the lake.

That feeling of gliding low over the water, with all the force of the beaufort scale behind me is how I imagine it is to be a swift. Today they swarmed over Low and High Maynard Reservoirs, a river of birds chasing the very air.

The Maynard Reservoirs - named after a prominent Essex family - are arguably the least auspicious on the reserve for wildlife. At one end lies a busy road, and the roads are busy in London once again. Compounding this, a public path down one side and a causeway popular with anglers in between both lakes, all with little vegetation to act as a screen, means the levels of human disturbance are high.

But, whatever the reason, they are favoured by the swifts this summer. Compared to a few days ago, the amount of insect life in the air seems greatly reduced, but presumably there is still a feast to be had. The Maynard Reservoirs’ location — downwind of the more elevated and gustier Lockwood reservoir — may mean that they act as a safe harbour for flies in need of sanctuary. What ensues is the aerial equivalent of Whales, sharks and tuna decimating a sardine bait-ball.

I devour the movements of a single swift, tracking it through my binoculars as it does laps around the lake. Each twist and turn needs storyboarding and turning into a graphic novel. It is all wing. All scythe-bladed wing. Its body is but a vessel for their determination to accelerate it and its wide mouth after some insect. All to sustain them in their whirring.

Dark as dirt, were it not for its genius shape and speed it wouldn’t be much to look at. This one has a whiter chin than most and, catching the sun as it rolls, its underwing sometimes appears pale brown, or even glosses whitish. On its closer transits I sometimes see a trailing edge to the wing destabilise, individual flight feathers trembling in the turbulent air.

I walk slowly along the causeway, where the swifts criss-cross between the two bodies of water. Cornering sharply to avoid sailing out into the road they stall, and turn upside down and inside out like a caught umbrella. Their forked tails briefly fan out into a rudder, then scissor shut again, in need of full-tilt, reckless speed. Sometimes they are left half open, dangling like little man legs.

Though each one moves as freely as an arrow, some unseen force — hunger for the flies too small to see — binds them and they gather, locust-like, in pockets of dense activity. Walking through this dream they slow-glide only a few feet away, tiptoeing on the breeze at my shoulder, fondling the air around my knees.

One comes so close I could wear it as a necklace, and all the clocks stop.

My heart broken, I turn for home, watching from my window as they take their dance into the evening’s thunderstorm.