Singing is the way that birds talk to each other. They sing to attract a mate or to defend its territory. It is the male bird that sings most of the songs. The female prefers to mate with a male that sings the best complex songs.
Some say that birds singing can also be a way for them to get rid of some extra fat. A bird that sings loud and for a long time while looking strong and healthy will show the female that he would make a good mate.
This wren is singing in different directions so that its singing can be heard all around him, front, back and sides