I remember a study of sorts done during the Rhodesian Bush War that indicated three problem areas for concealment {aside from the obvious, movement}. First was a white man's face. Second was his hands. That his hands are most likely to move is also to be taken into consideration.

And the third?

His rifle. It sticks out like a sore thumb and generally looks like nothing else in the bush. This all, mind you, relates to vision of people, not animals. Thus, the painting of various weapons during the war.

I REALLY wonder about coyotes. I find them to be pretty observant and they seem to be able to detect stuff other critters don't, meaning, they don't need movement to spook. I have no idea what they see, but I believe a timber yote has X-Ray vision, so I go Whole Hog when chasing them.

Amazing what long dark winters and boredome can do in the gun shop...