Very true, they also listen, my very first lurcher (pre locator days) would mark above where the ferret and rabbit were laid up, he'd scratch the ground above, he couldn't smell them so he must have listened, he was rarely wrong. I've never had a dog since who could do that.
Very good point that, on our last outing my dog was showing a lot of interest to a certain patch of grass, I stuck my hand through the grass and soil and pulled out a rabbit with a ferret attached to it, Had Col as my witness, bizarre...