Why do bird sing?
The main reason, male bird sing to attract mates (often, only males sing). Birds may also sing to communicate to their peers. For example a song can mean "This is my territory, you'd better not approach!". There are other reasons birds can sing (although I think I cited the two most important ones); you'll find much more information if you just google
why do birds sing?, there are plenty of very accessible online articles on the subject. Here is one such article that you may like reading
Talking about emotions is always difficult due to the absence of a good definition of what an emotion is. But anyway... yes, if females are attracted to the mates that sing well, it probably (depending on your definition) means it cause them to feel some emotions (sexual excitement for example).
Evolution of music in birds and humans
Bird song to attract mate (sexual selection). Humans, on the other hand, have evolved music production for different reasons (or at least this is what we think). The field of evolutionary musicology is a field in the junction between evolutionary psychology and biomusicology. In evolutionary musicology (and in evolutionary psychology) empirical testing is very complicated and therefore, today we can only think and make hypotheses but we can't test them. So always take with a grain of salt what you read in those fields.