Forward and downward flight visibility is one advantage
Three things:
1) a bird's head sits way out in front of it's wings, not underneath it cramped in a box hunched over (a la C172). I don't understand why people thing high wings have better visibility. Unless you want to look straight down they have garbage visibility in every other axis
2) I would argue birds are midwing flying wings, or blended wing designs
3) some designs are actually very similar, compare the B2 to an eagle:
Differences in wings are obvious since birds (mostly) all travel <100 knots and planes pretty much all travel well over that, but a few things carry over:
-hawks, owls, etc., have light serrations in the tips of their feathers to help keep sound down. The serrations on the 787 engines have the same goal, and achieve it the same by "mixing" the different velocity air more "gently"
-notice the "winglet" design on birds that require efficiency, IE, spend most of the day soaring, like hawks, they have a gentle upward curve like the A350, 787, etc.
-when birds dive they reduce their wingspan and "sweep" them back, so to speak (look up picture of diving birds, like Peregrine falcon).. B1, TU-160, F14, others, do this also
-birds have "hollow" bones, IE, they're interior design is honeycomb, we do the same in many aircraft structures to save weight but retain strength
I believe you'll find that 1,000s of years of evolution is not too different than what engineers give us when you look at the fundamentals in the design and the limitations and obvious differences in each