Thinking about the plane brought down by a flock of geese, and just wondering.

Obviously we can't just "get rid" of the geese. And deterrents don't seem to work.

I know NOTHING about aeronautics, so this is likely a dumb question, but here goes:

Why can't they put some kind of grill or grate over the part of the engine that sucks in the birds? There must be a reason why they can't, or they would have done so, but I'm wondering what it is?

Use layman's terms, please. I haven't even figured out what keeps airplanes in the air. I know they told me in school, but science wasn't my best subject. (Don't answer that one, just the bird one) Thanks!