A bird's-eye view is to look at something as though you were a bird in flight looking down.
For comic books and graphic novels, I've always found it to be one of the toughest perspectives to draw. The bird's-eye and worms's-eye views are staples of comic books, and I'm not talking about the metal bits in the spine unless we're discussing Doctor Octopus fighting Spider-Man.
The bird's-eye view gives a wide perspective of things that are below the characters and are used often to show great peril from falling from such a height and to showcase the setting, like New York City buildings in the background while Peter Parker's alter ego is swinging from building to building. Suddenly, you notice Doctor Octopus appeared on a rooftop below and is ready to hurl a giant air conditioner at our hero. The different perspective shows a depth of field the gives the illusion that the flat image is three dimensional. The sizes of the characters are different due to the distance from the viewpoint of the theoretical bird. We can see the edges of buildings converging to a horizon line far below us.
Bird's-eye view can give us a sense of danger, as though something is looming over our hero. Sometimes that danger is a crappy writer, but other times it may be Doctor Octopus is not working alone in this issue.
Iron Noder 2017