Descending from the Rhinogydd, I rested against an outcrop on the promontory that juts into the exquisite water-lily lake of Llyn Tecwyn Isaf, and waited to see what was happening here.

A grey heron soon came stalking round the shallow margins, aware of my presence, his suspicion allayed by my stillness. I wondered if he might be one of the nestlings I watched each day five years ago in the heronry among the larches in the shelter of Harlech Castle? To see (and hear – herons are very vocal birds) the whole process of their rearing at close quarters over several months was an enthralling experience. Those fledglings’ parents would surely have fished in this teeming pool before labouring back against the wind to disgorge the contents of their crops into the ramshackle, stinking nest while the young birds kept up their bizarre, cacophonous repertoire.

That cycle’s beginning again right now, the heron fiercely intent on his fishing, to feed his sitting mate. As I watch, he strikes, comes up with a flash of silver in his beak and juggles it down – a small trout, perhaps, or a gudgeon. A splash behind him momentarily distracts. He peers round. A drake goosander has alighted on the lake and is swimming rapidly towards him. I focus my glass, see the dark green of his crown, the faint early-spring flush of pink across his ivory flanks, the teddy-boy greased-down head-plumage. He scuds across to the heron, dives in the deeper water a few metres away, and he too comes up holding a silver fish.

The heron returns to his task – another stab, another fish. And for the goosander too, another fruitful brief dive. I have the clear impression that there is communication between the two birds. Fish shaken down into gullets, the heron stands motionless while the goosander dips under the surface again, re-surfacing seconds later 10 metres away. Luckless this time, he sails across the pond. The heron watches, then breaks into an awkward, splashy run through the shallows to the goosander’s new fishing place, where both birds again strike lucky. Teamwork? I think so.

