Mockingbird vs Wren

Lazy early morning, no walks. Taking a look at the rear window for around half an hour, I could register an interesting fight between a Wren and a Mockingbird. There was no fight indeed: Mockingbird is bigger and more agressive than the Wren. The Wren is always singing, wherever he is: on the antenna or on the lightning rod. And the Mockingbird (that also can sing very well) didn't want to see him singing and was always chasing him. And the pigeon was just resting...