Is "bird's eye point of view" considered informal?
In my opinion, it is fine to use this phrase in a scientific paper, but there are other better ways to convey this. "A Bird's Eye View" or "a bird's eye point of view" can be confused with a top-down view. I think the word you are looking for is "overview".
Alternately, you could say a strategic (or high-level, as opposed to tactical or low-level) view; more concerned with the bigger picture and goals than the details of how to accomplish them.