Unintentional camouflage

Whilst gazing upwards, I saw a flash of yellow as a bluetit disappeared into a hole in the neighbouring pebble-dash wall.

It then poked its head out as you see in the photo.

If you can see it, that is.

I wonder if it is intending to nest there or gathering wall insualtion for a nest or perhaps some insect or other.

I will have to keep an eye on the small hole in the wall.