As dusk falls on a warm October evening, I gradually become aware of a strange, high-pitched sizzling noise. From our table outside a busy bar, with Spaniards celebrating their national holiday, it reminds me of water carelessly tossed into a scorching frying pan.

I approach a bougainvillea bush decked with rich purple flowers, and the collective clamour separates into distinct notes. I realise I am listening to hundreds – perhaps thousands – of house sparrows, each bird calling frantically to their companions as they gather to roost for the night. It’s a sound I haven’t heard for more than 50 years.

Suzanne and I are celebrating our silver wedding anniversary in the town square of Sanlúcar de Barrameda in the far south-west of Spain, where Ferdinand Magellan and his fleet set sail in the autumn of 1519 on a voyage that would become the first circumnavigation of the world.

We’ve seen some far more exotic species than sparrows on our travels through Andalucía. Elegant lesser kestrels perching on the Giralda, the famous bell tower of Seville Cathedral; a dozen hoopoes poking their long, curved bills into the short turf at a local park; and noisy flocks of ring-necked parakeets tearing across the sky, reminding us of London.

Yet for me, this evening chorus of tuneless yet oddly charming sounds was the birding highlight of the trip. It took me right back to my suburban childhood, when I last encountered house sparrows in such vast – and noisy – numbers.