For Ian Harrison: I used to do the WBBS survey ( ?2010-2014 roughly)which included Pont Llanio and regularly recorded WT in the area from the disused factory up river to the open sheep fields, even found a nest with young in a thin dead tree on the edge of the river. They are elusive and sometimes I cheated a bit by waiting around to see/hear them. Not sure why this wouldn't be in the WBBS database.
Spotted Fly nested near the bridge but they went with the 'improvements' which were made to the bankside . Sand Martins attempted to nest in the very low river cliff near the Roman Fort fishermen's bridge, needless to say they failed as the bank regularly collapsed. The disused factory had good scrub all around which provided nest sites for Garden warbs, Blackcap and Bullfinch so I hope that still exists after the wrecking efforts of the railway enthusiasts.
The Common Sand, Dipper and Kf records were mine all seen at the rapids on the bend upstream of the factory. Swans and a sedge warbler were regularly breeding near the south end of the transect but swans often failed due to floods according to the landowner Mr Evans. The Sedge Warb habitat, a tiny scrap of marshy land with Hemlock water dropwort , docks, rushes, meadow sweet and ragged robin, was cleared for whatever reason. The lack of edge vegetation meant that the moorhen nested on a low overhanging branch which was vulnerable to flood and was so exposed made an easy target for predators.
I would like to think that the habitats along the river have been improved or just neglected to support those species but I won't hold my breath!