Side affect of lock down

We have a flower trough on the wall just outside our front door. It had several geraniums of differing colours that survived the winter and are now growing and flowering very well.
Yesterday we found this nest has been built in the corner of the trough.  We don't know how long its been there, we had not noticed any bird building activity. Obviously we must have only used the back door for some time and have not had many visitors lately.
Unfortunately the nest appears to be unoccupied so its owner probably found a property in a more suitable location.