What is real, what is reflection ?

Have you ever wondered if what you are looking at is just a reflection ?

I have been wondering for some time, what is reflection, what is real, who am I seeing when I look at mirror. Looks like I am not the only one ? This bird spent 4 hours fighting with hers reflection in mirror, trying to secure her territory, then owner came and drove of with reflection... Territory secured ?

I know image could be better, but I am amateur photographer so it is as is.