I was in a Barnes and Nobel book store one day just browsing around.. I came upon a book about birds.. I really should have purchased the book because it was that good.. Anyway.. I was reading about their anatomy and found out a couple of interesting things.. First off, their eye sight is about the best there is in the animal world.. Not only do they see color but they almost have super vision. All birds have this ability.. Eagles have eyes the size of a human... and their body size is so much smaller.. Then can see a rodent on the ground from hundreds of fee in the air..
I didn't see why Greys Dilate their pupils. But I know they do it when they are excited..
The other thing I learned that day is something about the way birds breathe.. You see, you and I breath into our lungs and then exhale.. Birds have a special system that allowes the air to flow through their lungs.. continuously... so the are extracting oxygen out of the air way more efficiently then other animals ever could...
Now when I see a flock of birds flying I don't think, How can they do that without getting tired.. They can because of the way they process oxygen from the air and then to their muscles...
This is a good question Beccy.. I am sure some of our family member can add to the eye thing...