A bird nest on the back wall of a cabin

My sister found this nest on the wall of a summer cabin. There were four young birds in the nest - here only one plus the mother bird can be seen. I do not recognise different species of birds, but this may be some kind of thrush?

Today the weather was even better than yesterday - almost 30 degrees Centigrade, We went out to play tennis again and swimming in the lake afterwards, mmmm.