There was a show about bird vision on Discovery a few years back.
At the very back of the retina, birds have this sort of "dimple" formation, packed with visual receptors.
The net result is that for the peripheral vision of birds, everything is seen as normal. But for a small circular section in the center of their field of vision, everything is magnified. So if they look straight at something, they "zoom in" on it.
I'm thinking my husband watches too many comic-book movies around me. I read this stuff and now the first thing I think of is, "Wow! that'd make a cool superhero trait!"