Grey Wagtail (Motacilla cinerea)

From last Septermber, heavy crop of a bird some way off. It's feeding on the roof of a small electricity substation behind our block. I learned only fairly recently that, outside the breeding season, the species is often attracted to such roofs in towns and cities, as rainwater can collect there. I guess they're after invertebrates. For me, they are perhaps the most elegant of bird species.