Yesterday, during a lengthy downpour, I noticed lots of birds outside my top floor window, it seemed odd how they were focused on the front of my house.
I opened the window looked outside and was surprised to see dozens of birds clinging to a very narrow feature on my wall, there wasn't enough space for them all so those still flying tried to muscle in and displaced others, lots of activity. Opening the window and being only 2m from them didn't seem to scare them.
I went outside to get another picture and noticed the even stranger view of dozens more birds clinging to the mortar channels in the brick work of the chimney.
I used the Merlin identifier app and it came up with a few possibilities; coal tit, juvenile house martin and the bank swallow.
My son has just shown me an area approximately 150m from the house where extensive ground work has happened this week, clearing a drainage ditch bank and felling some trees. Seeing the exposed banks of the ditch I now wonder if the bank swallow is likely given their home has been disturbed.
Bank Swallow is the US name for Sand Martin (UK), hence Merlin (an American slanted app) suggesting it (I think you can select a more local database assuming you're UK based... Western Palearctic or something I believe). I have a feeling the vast majority of our sand martins will have migrated by now, which makes me think you have House Martins. Someone better than me at ID's will hopefully be along to help or verify :o)
I would say House Martin - I saw huge numbers doing circuits and bumps this time last year - seemed to mainly youngsters practicing skills and feeding up before migration
Cin J