Right to left side? What does that mean exactly? [Also Google should have your answer]
Most bird omens I know are negative, like a bird flying into a house or a window someone will die. Different types of birds also have different tales. Birds flying left to right warns misfortune I think. Of course birds fly, unless it's a penguin why are you concerned at the flight patterns of birds?
What type of bird is it? and where did you see it flying. It is true many bird omens can be bad but not all of them, some of them are warnings others are messages, and sometimes birds are just birds. There needs to be a little more context to your question.
Ive had birds fly by real close to me, usually when im messing around with my frequencies.
though it depends what type of bird.
reading the movements of birds can be traced back to early civilizations, I think the most famous practitioner of this art is Teiresias, the a prophet of Thebes. being a blind man a young boy described the flying patterns of birds to him. He was then able to make accurate predictions.
overall, small birds bring smaller omens, while the large birds offer much more important messages.