Tha needs to get to Hebden Brig, lad. Earlier this week we spotted a flock of twenty or thirty birds flitting in and out of the tendrils of the creeper that cloaks the mill in the centre (no Innovations - do you know it?). It was dusk but after a while I was able to ascertain that they were all wagtails of one kind or another. Never seen anything like it, though I believe there is at least one huge roost in a city, maybe London.