A circlage of house martins

It's not often something will catch my eye over drifting fog.  But, as we left the Cow and Calf today, this flock of birds did.

I watched them for ages grouping together on this rock face and one round the corner.  There were over 200, I reckon, in total. I'm wondering if they're pausing on migration, gathering before they set off or avoiding tomorrow's gales.  They would pause for some time and then all swoop of together, circle round and head straight back to the rock again.

Whatever they were doing, they were beauties to watch and I've discovered a few of their wonderful collective noun names: circlage, flight, gulp, richness, and swoop


(#PRweather: ahead of storm Ali - house martins gather sheltering from the wind)