On a cooling evening I walked down to the Dwyryd estuary. The track ran through fields that were won from the sea two centuries ago, in the early stages of the great reclamation schemes around this country, which culminated in the Cob embankment between Aber Iâ and Porthmadog. This is good farming land now. The first hay crop is already gathered in, the air heavy with its scent, which mingles with honeyed fragrance of meadowsweet growing in profusion along western banks of ruler-straight drainage channels choked with rushes and duckweed. It was very quiet. A lesser horseshoe bat zig-zagged close by in the dimity light. Swifts flew high above, their screaming a barely audible scratchiness. A bright half-moon had emerged from behind the Rhinogydd range to describe a slow arc of ascent southerly. Hill detail was already lost in indigo shadow. Above Moel Ddu’s cleft summit the first stars glimmered hazily. To the north, the elegant pyramid of Yr Wyddfa – Snowdon, if you must (but never “Mount Snowdon”) – lent symmetry to this finest of Welsh panoramas. A resounding racket suddenly rose from beyond the sea defences. Gulls from the small colony on Glastraeth saltings screamed and skirled their obvious displeasure. I headed in that direction to see what was troubling them. Focusing my glass from on top of the embankment I saw an animal, large polecat-sized, raiding the nests. Parent birds were dive-bombing it, pulling out at the last moment as it reared on hind legs to chitter angrily at them. In its mouth it held a downy chick. It bounded over the sea wall and ran rapidly across the newly cut hayfield toward sturdy oak trees along the farther field margin. Gulls followed furiously. It was surely one of the Mustellidae. As to which species, I was more certain of what it wasn’t than what it was. Too large for a stoat, it lacked the white bib and black tip to the tail. Its pelage was rich russet, its chin splashed with white. Reaching the largest boundary oak, it disappeared suddenly – perhaps into a tree-hole. I think it was an American mink (Neovison vison) – which is bad news for the local birds and rabbits; but its alien presence certainly added wildness to the evening’s calm beauty.