SThe late afternoon light over the bay caused me to slip and run past the sea defenses past the mill pond in Ynys to Llech Ollwyn. There I sat on one of the benches and looked across the river mouth to But Ia, got out a bottle and binoculars and waited for the developments. The flood had drained Traeth Bach. The western sun added a touch of lushness to the sensuality of curved sandbars and enhanced the brilliance of rippled water and curved sand. All the low hills along the Ll penn Peninsula – Yarn Fadryn, Yarn Yarn, Yr Eifl, the bulky little Moel-y-Gest in the foreground – glided behind a shimmering, pointillist veil that moved quickly in my direction.

I focused on the telescope and looked in the mouth for traces of bird life, which was once so numerous at this time of the year. Years ago, when I saw huge swarms of pigtail tails, I noticed a small group of birds gathering on a low sand ridge over a meandering deep channel. The biggest bird's retro-bill, a hint of dove gray and rusty red along the thick neck, identified it: rain geese! Diver with red throat. A few teenagers and one adult, still in their beautiful summer dress, set off early from their breeding grounds to the northern Scottish Lochans. A neat bunch of oystercatchers flew up to spray beside them.

Larynx jumper with chicks

"The biggest bird's retro-bill, a hint of dove gray and rusty red along the thick neck, identified it: rain geese!" Photo: David Robinson / Alamy

Somewhere far out at the mouth of the river, a lonely curlew, who had descended from nesting in the wild bogs, persistently shouted the two notes from which his name came. No answer came in a place where, 40 years ago, a species of thousands of people floated in the air and ecstatically swirled their song up and down.

The present, invisible, lonely presence in the shimmering light, the memory of the crowd here, felt somehow spooky. I watched as clouds hid the western hills. Fluctuating columns of mercury dissolved and moved across the water toward me. A double rainbow was suddenly flung east over high hills, its end almost at my feet. Two redshanks raced by and scolded with a warning. Strong raindrops fell. I fled home from the flood.