I love the ambiguity of the question! So many variables in such a small amount of room!
Are we talking area, or end to end, or side to side, or diagonal?
Bald eagles: adult, or immature? Male, or female? Footprint, or height, or wingspan length, or volume (in case we are painting the field, maybe we're just painting the lines on the field with bald eagle goo??), or maybe we're covering the field with their feathers?
It probably isn't a kicking-football pitch because it isn't really called a field, so are we talking throwing-football, CFL? NFL? another league I am not familiar with?
I am genuinely tickled, and quite content to never being able to answer the question
Well, in freedom units it is a bald eagle, and an NFL football field.
I would imagine its wingspan per cheeseburger, and when counting the small lengths we need to convert to bullets (which ironically goes back to metric; 50mm, 35mm, 9mm etc.)
I would also assume we are talking about length because that is the main topic (or was, I should say), and we don't want to confuse with liquids or weight.