A flock of wagtails

I was walking back through the large car park near home just after sunset when I was surprised to see hundreds of small birds on the ground, all uniformly distributed with a bit of space to themselves and not really doing much other than standing where they were.

There were enough of them to occupy most of the back half of the car park, and in the low flat light of dusk it made for a strange sight, like the first portentous sign that something strange is going on in an apocalyptic movie.

On closer inspection they turned out to be Pied Wagtails, one of the friendliest and least sinister birds I can think of, and I've since learned that they do often gather in large flocks at dusk to roost together. I've been back a few times since at the same time of day to see them again.