Here's what goes through my mind...
Oh that sounds like a deer, it's definately a deer, let me just take a peek and then get ready. I crane around the tree to find the deer and it's a squirrel. [&:]
More than once, I've sat there and said, that's definately a squirrel. I'm not going to waste any movment, and just sit still. I finally take a look in the direction, and what do you know, it's a deer, now closer than I'd like

.
That's how things go for me. [8D]